Michael Kirschfink - Academia.edu (original) (raw)
Papers by Michael Kirschfink
Fifteen premature newborns with hyaline membrane disease causing acute respiratory distress were ... more Fifteen premature newborns with hyaline membrane disease causing acute respiratory distress were evaluated for complement activation. A high intrapulmonary right-to-left shunt and marked arterial-alveolar oxygen difference indicated the severity of the respiratory failure. Twenty preterm healthy infants served as controls. Total haemolytic activity, plasma concentrations of complement components and regulatory proteins (C3, C4, C1-inhibitor, factors H and I) as well as activation products (C3a, C3dg, C1rsC1-inhibitor, C3b(Bb)P) gave no evidence of significant complement activation. Functional activity of the ubiquitous regulatory protein C1-inhibitor was significantly reduced without impact on classical pathway activation. These data suggest that, in contrast to the adult form of respiratory distress syndrome, the low-pressure pulmonary oedema characterising hyaline membrane disease is not mediated by activation of the complement system.
Oncoimmunology, 2015
Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by therapeutic... more Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by therapeutic anticancer monoclonal antibodies (mAbs). However, the efficacy of antibodies is limited by the resistance of malignant cells to complement attack, primarily due to the over-expression of one or more membrane complement regulatory proteins (mCRPs) CD46, CD55, and CD59. CD20-positive Burkitt lymphoma Raji cells and primary CLL cells are resistant to rituximab (RTX)-induced CDC whereas ofatumumab (OFA) proved to be more efficient in cell killing. Primary CLL cells but not CD52-positive acute lymphoblastic leukemia (ALL) REH cells were sensitive to alemtuzumab (ALM)-induced CDC. Upon combined inhibition on Raji and CLL cells by mCRPs-specific siRNAs or neutralizing antibodies, CDC induced by RTX and by OFA was augmented. Similarly, CDC of REH cells was enhanced after mCRPs were inhibited upon treatment with ALM. All mAbs induced C3 opsonization, which was significantly augmented upon blocki...
Journal of clinical immunology, 1997
One hundred sixty-six cases of primary immunodeficiency diseases (PID) (95 males, 71 females), di... more One hundred sixty-six cases of primary immunodeficiency diseases (PID) (95 males, 71 females), diagnosed according to WHO criteria, have been registered at the Children's Hospital, University of São Paulo, Brazil. The following frequencies were found: predominantly humoral defects, 60.8% (n = 101); T cell defects, 4.9% (n = 8); combined ID, 9.6% (n = 16); phagocyte disorders, 18.7% (n = 31); and complement deficiencies, 6% (n = 10). IgA deficiency was the most frequent disorder (n = 60), followed by transient hypogammaglobulinemia (n = 14), chronic granulomatous disease (n = 14), and X-linked agammaglobulinemia (n = 9). In comparison to other (national) reports, we observed higher relative frequencies of phagocyte and complement deficiencies. Recurrent infections were the cause of death in 12.7%. Allergic symptoms were observed in 41%, mainly in IgA-deficient, hypogammaglobulinemic, or hyper-IgE patients, and autoimmune disorders in 5%, predominantly in IgA and complement defici...
Complement and inflammation, 1991
While preformed BSA-anti-BSA immune complexes (PIC) bind efficiently to human RBC after their int... more While preformed BSA-anti-BSA immune complexes (PIC) bind efficiently to human RBC after their interaction with human complement, nascent BSA-anti-BSA immune complexes (NIC) formed in the presence of complement do not bind to autologous RBC. The same results were obtained with tetanus toxoid-anti-tetanus toxoid PIC and NIC. In order to elucidate the causes of this marked difference between the RBC-binding properties of PIC and NIC, the profile of complement activation induced by them was compared using haemolytic assays and sensitive ELISA tests. BSA-anti-BSA NIC activated C1 more efficiently than PIC. This was reflected in a higher C4 content of the isolated NIC and higher C1 INH-C1s and lower C1q-fibronectin complex level in the NIC-treated serum as compared to the PIC-treated ones. Although isolated NIC contained more C3 than isolated PIC did, there was no significant difference in the AP activation. These findings suggest that the failure of NIC to bind to RBC is not due to a lac...
Molecular immunology, 2014
Complement deficiencies comprise between 1 and 10% of all primary immunodeficiencies (PIDs) accor... more Complement deficiencies comprise between 1 and 10% of all primary immunodeficiencies (PIDs) according to national and supranational registries. They are still considered rare and even of less clinical importance. This not only reflects (as in all PIDs) a great lack of awareness among clinicians and general practitioners but is also due to the fact that only few centers worldwide provide a comprehensive laboratory complement analysis. To enable early identification, our aim is to present warning signs for complement deficiencies and recommendations for diagnostic approach. The genetic deficiency of any early component of the classical pathway (C1q, C1r/s, C2, C4) is often associated with autoimmune diseases whereas individuals, deficient of properdin or of the terminal pathway components (C5 to C9), are highly susceptible to meningococcal disease. Deficiency of C1 Inhibitor (hereditary angioedema, HAE) results in episodic angioedema, which in a considerable number of patients with id...
Journal of thrombosis and haemostasis : JTH, 2014
ABSTRACT Atypical hemolytic uremic syndrome (aHUS) is characterized by mechanical hemolysis, plat... more ABSTRACT Atypical hemolytic uremic syndrome (aHUS) is characterized by mechanical hemolysis, platelet consumption and renal impairment. Dysregulation of the complement system with emphasis on the alternative pathway (AP) represents in most cases the underlining pathophysiology in aHUS in contrast to infection due to enterohemorrhagic Shiga-like toxin producing Escherichia coli in typical diarrhea -associated HUS [1, 2]. Since 2009 the treatment with eculizumab (SolirisTM, Alexion Pharmaceuticals Inc, Cheshire, CT, USA) has become a valuable lifesaving therapeutic option beyond plasma therapy for many aHUS patients. This article is protected by copyright. All rights reserved.
Journal of clinical immunology, 1997
Previous reports provided evidence of an immunosuppressive role of natural anti-F(ab')2 antib... more Previous reports provided evidence of an immunosuppressive role of natural anti-F(ab')2 antibodies. If suppressive anti-F(ab')2 antibodies also regulated the autoantibody production in cold agglutination, one would expect high titers of anti-F(ab')2 to be associated with low titers of cold agglutinins. Indeed, our previous studies revealed an inverse correlation between IgG-anti-F(ab')2 and cold agglutinins. Many previous experiments focused on anti-F(ab')2 of an antiidiotypic nature. Recent epitope mapping showed that anti-F(ab')2 of healthy persons is not an antiidiotype but recognizes a hinge region sequence. We attempted to answer the question whether this IgG-antihinge antibody is responsible for the previously described association between anti-F(ab')2 and cold agglutinins. IgG-antihinge and IgG-anti-F(ab')2 antibody was determined and statistically analyzed in the serum of 334 patients with cold agglutination. Our experiments revealed a strong ...
Journal of immunology (Baltimore, Md. : 1950), Jan 15, 1995
To shed light on the molecular basis of two different types of complete C1q deficiency, we perfor... more To shed light on the molecular basis of two different types of complete C1q deficiency, we performed extensive Southern blot analysis and sequenced all exons of the genes coding for the A, B, and C chains of C1q on two groups of deficient patients. In one family with three cases of complete C1q deficiency we found a point mutation in the codon for glutamine (CAG) at position 186 of the A chain that led to a termination codon (TAG). No gene products of any of the three genes were found in the patients' sera, indicating that full length polypeptides of the A, B, and C chains are required to form and secrete functional C1q. A second point mutation was found in a patient with a complete functional C1q defect. The abnormal C1q molecule had been shown to have a low m.w. of approximately 150,000 and a sedimentation coefficient of below 7S. The mutation occurred in the codon for glycine in position 6 of the C chain where a single base exchange (G-->A transition) has led to an arginin...
Clinical and experimental immunology, 1987
The C3 fragment C3a belongs to the anaphylatoxins. It has immune regulatory activity and contribu... more The C3 fragment C3a belongs to the anaphylatoxins. It has immune regulatory activity and contributes to the pathogenesis of the adult respiratory distress syndrome (ARDS). The low molecular weight (9 kD) of C3a complicates the production of antibodies to C3a. We obtained a monoclonal antibody (designated H13) to human C3a. It reacts with C3a or C3a-desArg and with native C3 but not with C5 or C5a. In immunoblot analysis it reacts with the alpha- but not with beta-chain of C3 and binds to a protein with a mol. wt of about 10 kD present in zymosan-activated sera which is only marginally detectable in nonactivated serum and absent in plasma. H13 crossreacts with the analogous proteins of rabbit, guinea pig and sheep. H13 has the capacity to bind 125I-radiolabelled C3a efficiently but fails totally to react with 125I-C5a or with other C3 alpha-chain fragments. H13 blocks C3a functional activity. It markedly inhibits C3a-induced 3H-serotonin release from platelets in vitro and similarly ...
The International journal of artificial organs, 1991
Studies were made to compare completely heparin-bonded (HBS) and conventional extracorporeal circ... more Studies were made to compare completely heparin-bonded (HBS) and conventional extracorporeal circulation surfaces using capillary membrane oxygenators (CMO) in sheep and dogs for up to five days. The aims were: to investigate the need for systemic heparinization in the case of heparin-coated surfaces, to assess blood compatibility and gas exchange performance of both systems and the extent of complement activation, and to find solutions for plasma leakage by the use of CMO. All studies were performed under standardized conditions, such as drugs, surgery, priming, blood flow rate etc. For heparin-coated surface studies all blood interfaces (CMO, catheters, tubes, etc) were coated. It was possible to eliminate systemic heparinization totally when HBS were used. During the five-day non-heparin application period blood coagulation parameters were almost unchanged and in the physiological range, platelets did not drop below 80%, hemolysis was negligible and gas exchange performance was u...
Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen, 2008
Many faculties worldwide apply the method of problem-based learning (PBL) in their curricula as a... more Many faculties worldwide apply the method of problem-based learning (PBL) in their curricula as a form of instruction by which students in small groups develop problem-solving strategies on the basis of a specific case. This approach fosters self-responsible and context-dependent learning, which aims at providing an improved anchoring of knowledge. For this reason, the previous decades have seen a distribution of the method to medical schools across the world. The role of the tutor assumes particular importance since, in contrast to the traditional university system, he or she serves as a facilitator who fosters and structures content-related and group-dynamic learning processes. In some cases, this requires an intervention by the tutor. The major challenge is to intervene at the right time and in an appropriate manner. This paper presents examples of difficult PBL situations using short film sequences to demonstrate and comments on potential approaches of the tutor in attempting to...
International Journal of Medical Microbiology Supplements, 2004
Complement activation plays an important role in the elimination of invading microorganisms. Borr... more Complement activation plays an important role in the elimination of invading microorganisms. Borrelia (B.) burgdorferi sensu lato the etiological agent of Lyme borreliosis, can resist complement-mediated killing. The mechanism of complement resistance of B. burgdorferi sensu stricto apparently depends on the expression of several outer surface proteins described as CRASPs (complement regulator-acquiring surface proteins). These borrelial surface proteins are able to bind components of the complement regulatory system, factor H and/or factor H-like protein 1 (FHL-1), two crucial fluid-phase negative regulators of the alternative pathway of complement. It was previously demonstrated that one CRASP is encoded by a member of the erp gene family. The purpose of the study was to use a set of monoclonal antibodies (mAb) and polyclonal antisera to characterize the relatedness of factor H-binding CRASP and Erp proteins among several B. burgdorferi sensu stricto and B. afzelii strains. Based on the observed cross-reactivities between B. burgdorferi sensu stricto strains LW2 and PKa-1, it is concluded that BbCRASP-3 is similar to ErpP, BbCRASP-4 is structurally related to ErpC, and BbCRASP-5 is similar to ErpA. The BaCRASP-2 and BaCRASP-4 proteins of B. afzelii strain EB1 reacted with both anti-ErpA and anti-ErpP antibodies whereas BaCRASP-5 of B. afzelii strain FEM1-D15 exclusively reacted with BbCRASP-3/ErpP specific antibodies. Together, these data indicate that most of the factor H-binding CRASPs are members of the Erp protein family, which represents a polymorphic class of proteins with similar or identical immunological reactivities.
Pediatric Nephrology, 2014
Eculizumab is a humanized anti-C5 antibody approved for the treatment of atypical hemolytic uremi... more Eculizumab is a humanized anti-C5 antibody approved for the treatment of atypical hemolytic uremic syndrome (aHUS). Its use is increasing in children following reports of its safety and efficacy. We reviewed biochemical and clinical data related to possible drug-induced liver injury in 11 children treated with eculizumab for aHUS in a single center. Elevated aminotransferases were observed in 7 children aged 6 to 11 years following eculizumab treatment for aHUS. Internationally accepted liver enzyme thresholds for drug-induced liver injury were exceeded in 5 cases. In all cases, liver injury was classified as mixed hepatocellular and cholestatic. Infectious and other causes were excluded in each case. One patient with no pre-existing liver disease developed tender hepatomegaly and liver enzyme derangement exceeding 20 times the upper limit of normal following initiation of eculizumab. Recurrent liver injury following re-challenge with eculizumab necessitated its discontinuation and transition to plasma therapy. Hepatotoxicity in association with eculizumab is a potentially important yet previously unreported adverse event. We recommend monitoring liver enzymes in all patients receiving eculizumab. Further research is required to clarify the impact of this adverse event, to characterize the mechanism of potential hepatotoxicity, and to identify which patients are most at risk.
Targeted Oncology, 2014
The overexpression of membrane-bound complement regulatory proteins (mCRP; CD46, CD55, CD59) prev... more The overexpression of membrane-bound complement regulatory proteins (mCRP; CD46, CD55, CD59) preventing opsonization and complement-dependent cytotoxicity (CDC) is considered a major barrier for successful antibody-based cancer immunotherapy. To avoid a potential deleterious effect of mCRP neutralization on normal tissue cells, complement regulation has to be selectively targeted to the malignant cells. In this study, anti-mCRP small interfering RNAs (siRNAs) were encapsulated in transferrin-coupled lipoplexes for the specific delivery to transferrin receptor CD71(high) expressing BT474, DU145, and SW480 as well as corresponding CD71-knockdown (CD71(low)) tumor cells. Targeted delivery with transferrin-siRNA-lipoplexes became possible by charge neutralization and resulted in efficient silencing of all three mCRPs up to 90 %, which is dependent on their CD71 expression. The mCRP knockdown led to a significant increase of CDC on CD71(high) tumor cells by 68 % in BT474, 58 % in DU145, and 40 % in SW480 cells but only slightly increased on CD71(low) cells. Downregulation of CD46 and CD55 significantly increased C3 opsonization only on CD71(high) tumor cells. Our results demonstrate for the first time that by specific delivery of anti-mCRP siRNA through transferrin receptor, complement regulation can be selectively neutralized, allowing specific antibody-mediated killing of tumor cells without affecting healthy bystander cells, which appears to be a suited strategy to improve antibody-based cancer immunotherapy.
OncoImmunology, 2015
ABSTRACT Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by th... more ABSTRACT Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by therapeutic anticancer monoclonal antibodies (mAbs). However, the efficacy of antibodies is limited by the resistance of malignant cells to complement attack, primarily due to the over-expression of one or more membrane complement regulatory proteins (mCRPs) CD46, CD55, and CD59. CD20-positive Burkitt lymphoma Raji cells and primary CLL cells are resistant to rituximab (RTX)-induced CDC whereas ofatumumab (OFA) proved to be more efficient in cell killing. Primary CLL cells but not CD52-positive acute lymphoblastic leukemia (ALL) REH cells were sensitive to alemtuzumab (ALM)-induced CDC. Upon combined inhibition on Raji and CLL cells by mCRPs-specific siRNAs or neutralizing antibodies, CDC induced by RTX and by OFA was augmented. Similarly, CDC of REH cells was enhanced after mCRPs were inhibited upon treatment with ALM. All mAbs induced C3 opsonization, which was significantly augmented upon blocking mCRPs. C3 opsonization led to enhanced cell-mediated cytotoxicity of leukemia cells exposed to PBLs or macrophages. Furthermore, opsonized CLL cells were efficiently phagocytized by macrophages. Our results provide conclusive evidence that inhibition of mCRPs expression sensitizes leukemic cells to complement attack thereby enhancing the therapeutic effect of mAbs targeting leukemic cells.
Molecular Immunology, 2010
Fifteen premature newborns with hyaline membrane disease causing acute respiratory distress were ... more Fifteen premature newborns with hyaline membrane disease causing acute respiratory distress were evaluated for complement activation. A high intrapulmonary right-to-left shunt and marked arterial-alveolar oxygen difference indicated the severity of the respiratory failure. Twenty preterm healthy infants served as controls. Total haemolytic activity, plasma concentrations of complement components and regulatory proteins (C3, C4, C1-inhibitor, factors H and I) as well as activation products (C3a, C3dg, C1rsC1-inhibitor, C3b(Bb)P) gave no evidence of significant complement activation. Functional activity of the ubiquitous regulatory protein C1-inhibitor was significantly reduced without impact on classical pathway activation. These data suggest that, in contrast to the adult form of respiratory distress syndrome, the low-pressure pulmonary oedema characterising hyaline membrane disease is not mediated by activation of the complement system.
Oncoimmunology, 2015
Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by therapeutic... more Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by therapeutic anticancer monoclonal antibodies (mAbs). However, the efficacy of antibodies is limited by the resistance of malignant cells to complement attack, primarily due to the over-expression of one or more membrane complement regulatory proteins (mCRPs) CD46, CD55, and CD59. CD20-positive Burkitt lymphoma Raji cells and primary CLL cells are resistant to rituximab (RTX)-induced CDC whereas ofatumumab (OFA) proved to be more efficient in cell killing. Primary CLL cells but not CD52-positive acute lymphoblastic leukemia (ALL) REH cells were sensitive to alemtuzumab (ALM)-induced CDC. Upon combined inhibition on Raji and CLL cells by mCRPs-specific siRNAs or neutralizing antibodies, CDC induced by RTX and by OFA was augmented. Similarly, CDC of REH cells was enhanced after mCRPs were inhibited upon treatment with ALM. All mAbs induced C3 opsonization, which was significantly augmented upon blocki...
Journal of clinical immunology, 1997
One hundred sixty-six cases of primary immunodeficiency diseases (PID) (95 males, 71 females), di... more One hundred sixty-six cases of primary immunodeficiency diseases (PID) (95 males, 71 females), diagnosed according to WHO criteria, have been registered at the Children's Hospital, University of São Paulo, Brazil. The following frequencies were found: predominantly humoral defects, 60.8% (n = 101); T cell defects, 4.9% (n = 8); combined ID, 9.6% (n = 16); phagocyte disorders, 18.7% (n = 31); and complement deficiencies, 6% (n = 10). IgA deficiency was the most frequent disorder (n = 60), followed by transient hypogammaglobulinemia (n = 14), chronic granulomatous disease (n = 14), and X-linked agammaglobulinemia (n = 9). In comparison to other (national) reports, we observed higher relative frequencies of phagocyte and complement deficiencies. Recurrent infections were the cause of death in 12.7%. Allergic symptoms were observed in 41%, mainly in IgA-deficient, hypogammaglobulinemic, or hyper-IgE patients, and autoimmune disorders in 5%, predominantly in IgA and complement defici...
Complement and inflammation, 1991
While preformed BSA-anti-BSA immune complexes (PIC) bind efficiently to human RBC after their int... more While preformed BSA-anti-BSA immune complexes (PIC) bind efficiently to human RBC after their interaction with human complement, nascent BSA-anti-BSA immune complexes (NIC) formed in the presence of complement do not bind to autologous RBC. The same results were obtained with tetanus toxoid-anti-tetanus toxoid PIC and NIC. In order to elucidate the causes of this marked difference between the RBC-binding properties of PIC and NIC, the profile of complement activation induced by them was compared using haemolytic assays and sensitive ELISA tests. BSA-anti-BSA NIC activated C1 more efficiently than PIC. This was reflected in a higher C4 content of the isolated NIC and higher C1 INH-C1s and lower C1q-fibronectin complex level in the NIC-treated serum as compared to the PIC-treated ones. Although isolated NIC contained more C3 than isolated PIC did, there was no significant difference in the AP activation. These findings suggest that the failure of NIC to bind to RBC is not due to a lac...
Molecular immunology, 2014
Complement deficiencies comprise between 1 and 10% of all primary immunodeficiencies (PIDs) accor... more Complement deficiencies comprise between 1 and 10% of all primary immunodeficiencies (PIDs) according to national and supranational registries. They are still considered rare and even of less clinical importance. This not only reflects (as in all PIDs) a great lack of awareness among clinicians and general practitioners but is also due to the fact that only few centers worldwide provide a comprehensive laboratory complement analysis. To enable early identification, our aim is to present warning signs for complement deficiencies and recommendations for diagnostic approach. The genetic deficiency of any early component of the classical pathway (C1q, C1r/s, C2, C4) is often associated with autoimmune diseases whereas individuals, deficient of properdin or of the terminal pathway components (C5 to C9), are highly susceptible to meningococcal disease. Deficiency of C1 Inhibitor (hereditary angioedema, HAE) results in episodic angioedema, which in a considerable number of patients with id...
Journal of thrombosis and haemostasis : JTH, 2014
ABSTRACT Atypical hemolytic uremic syndrome (aHUS) is characterized by mechanical hemolysis, plat... more ABSTRACT Atypical hemolytic uremic syndrome (aHUS) is characterized by mechanical hemolysis, platelet consumption and renal impairment. Dysregulation of the complement system with emphasis on the alternative pathway (AP) represents in most cases the underlining pathophysiology in aHUS in contrast to infection due to enterohemorrhagic Shiga-like toxin producing Escherichia coli in typical diarrhea -associated HUS [1, 2]. Since 2009 the treatment with eculizumab (SolirisTM, Alexion Pharmaceuticals Inc, Cheshire, CT, USA) has become a valuable lifesaving therapeutic option beyond plasma therapy for many aHUS patients. This article is protected by copyright. All rights reserved.
Journal of clinical immunology, 1997
Previous reports provided evidence of an immunosuppressive role of natural anti-F(ab')2 antib... more Previous reports provided evidence of an immunosuppressive role of natural anti-F(ab')2 antibodies. If suppressive anti-F(ab')2 antibodies also regulated the autoantibody production in cold agglutination, one would expect high titers of anti-F(ab')2 to be associated with low titers of cold agglutinins. Indeed, our previous studies revealed an inverse correlation between IgG-anti-F(ab')2 and cold agglutinins. Many previous experiments focused on anti-F(ab')2 of an antiidiotypic nature. Recent epitope mapping showed that anti-F(ab')2 of healthy persons is not an antiidiotype but recognizes a hinge region sequence. We attempted to answer the question whether this IgG-antihinge antibody is responsible for the previously described association between anti-F(ab')2 and cold agglutinins. IgG-antihinge and IgG-anti-F(ab')2 antibody was determined and statistically analyzed in the serum of 334 patients with cold agglutination. Our experiments revealed a strong ...
Journal of immunology (Baltimore, Md. : 1950), Jan 15, 1995
To shed light on the molecular basis of two different types of complete C1q deficiency, we perfor... more To shed light on the molecular basis of two different types of complete C1q deficiency, we performed extensive Southern blot analysis and sequenced all exons of the genes coding for the A, B, and C chains of C1q on two groups of deficient patients. In one family with three cases of complete C1q deficiency we found a point mutation in the codon for glutamine (CAG) at position 186 of the A chain that led to a termination codon (TAG). No gene products of any of the three genes were found in the patients' sera, indicating that full length polypeptides of the A, B, and C chains are required to form and secrete functional C1q. A second point mutation was found in a patient with a complete functional C1q defect. The abnormal C1q molecule had been shown to have a low m.w. of approximately 150,000 and a sedimentation coefficient of below 7S. The mutation occurred in the codon for glycine in position 6 of the C chain where a single base exchange (G-->A transition) has led to an arginin...
Clinical and experimental immunology, 1987
The C3 fragment C3a belongs to the anaphylatoxins. It has immune regulatory activity and contribu... more The C3 fragment C3a belongs to the anaphylatoxins. It has immune regulatory activity and contributes to the pathogenesis of the adult respiratory distress syndrome (ARDS). The low molecular weight (9 kD) of C3a complicates the production of antibodies to C3a. We obtained a monoclonal antibody (designated H13) to human C3a. It reacts with C3a or C3a-desArg and with native C3 but not with C5 or C5a. In immunoblot analysis it reacts with the alpha- but not with beta-chain of C3 and binds to a protein with a mol. wt of about 10 kD present in zymosan-activated sera which is only marginally detectable in nonactivated serum and absent in plasma. H13 crossreacts with the analogous proteins of rabbit, guinea pig and sheep. H13 has the capacity to bind 125I-radiolabelled C3a efficiently but fails totally to react with 125I-C5a or with other C3 alpha-chain fragments. H13 blocks C3a functional activity. It markedly inhibits C3a-induced 3H-serotonin release from platelets in vitro and similarly ...
The International journal of artificial organs, 1991
Studies were made to compare completely heparin-bonded (HBS) and conventional extracorporeal circ... more Studies were made to compare completely heparin-bonded (HBS) and conventional extracorporeal circulation surfaces using capillary membrane oxygenators (CMO) in sheep and dogs for up to five days. The aims were: to investigate the need for systemic heparinization in the case of heparin-coated surfaces, to assess blood compatibility and gas exchange performance of both systems and the extent of complement activation, and to find solutions for plasma leakage by the use of CMO. All studies were performed under standardized conditions, such as drugs, surgery, priming, blood flow rate etc. For heparin-coated surface studies all blood interfaces (CMO, catheters, tubes, etc) were coated. It was possible to eliminate systemic heparinization totally when HBS were used. During the five-day non-heparin application period blood coagulation parameters were almost unchanged and in the physiological range, platelets did not drop below 80%, hemolysis was negligible and gas exchange performance was u...
Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen, 2008
Many faculties worldwide apply the method of problem-based learning (PBL) in their curricula as a... more Many faculties worldwide apply the method of problem-based learning (PBL) in their curricula as a form of instruction by which students in small groups develop problem-solving strategies on the basis of a specific case. This approach fosters self-responsible and context-dependent learning, which aims at providing an improved anchoring of knowledge. For this reason, the previous decades have seen a distribution of the method to medical schools across the world. The role of the tutor assumes particular importance since, in contrast to the traditional university system, he or she serves as a facilitator who fosters and structures content-related and group-dynamic learning processes. In some cases, this requires an intervention by the tutor. The major challenge is to intervene at the right time and in an appropriate manner. This paper presents examples of difficult PBL situations using short film sequences to demonstrate and comments on potential approaches of the tutor in attempting to...
International Journal of Medical Microbiology Supplements, 2004
Complement activation plays an important role in the elimination of invading microorganisms. Borr... more Complement activation plays an important role in the elimination of invading microorganisms. Borrelia (B.) burgdorferi sensu lato the etiological agent of Lyme borreliosis, can resist complement-mediated killing. The mechanism of complement resistance of B. burgdorferi sensu stricto apparently depends on the expression of several outer surface proteins described as CRASPs (complement regulator-acquiring surface proteins). These borrelial surface proteins are able to bind components of the complement regulatory system, factor H and/or factor H-like protein 1 (FHL-1), two crucial fluid-phase negative regulators of the alternative pathway of complement. It was previously demonstrated that one CRASP is encoded by a member of the erp gene family. The purpose of the study was to use a set of monoclonal antibodies (mAb) and polyclonal antisera to characterize the relatedness of factor H-binding CRASP and Erp proteins among several B. burgdorferi sensu stricto and B. afzelii strains. Based on the observed cross-reactivities between B. burgdorferi sensu stricto strains LW2 and PKa-1, it is concluded that BbCRASP-3 is similar to ErpP, BbCRASP-4 is structurally related to ErpC, and BbCRASP-5 is similar to ErpA. The BaCRASP-2 and BaCRASP-4 proteins of B. afzelii strain EB1 reacted with both anti-ErpA and anti-ErpP antibodies whereas BaCRASP-5 of B. afzelii strain FEM1-D15 exclusively reacted with BbCRASP-3/ErpP specific antibodies. Together, these data indicate that most of the factor H-binding CRASPs are members of the Erp protein family, which represents a polymorphic class of proteins with similar or identical immunological reactivities.
Pediatric Nephrology, 2014
Eculizumab is a humanized anti-C5 antibody approved for the treatment of atypical hemolytic uremi... more Eculizumab is a humanized anti-C5 antibody approved for the treatment of atypical hemolytic uremic syndrome (aHUS). Its use is increasing in children following reports of its safety and efficacy. We reviewed biochemical and clinical data related to possible drug-induced liver injury in 11 children treated with eculizumab for aHUS in a single center. Elevated aminotransferases were observed in 7 children aged 6 to 11 years following eculizumab treatment for aHUS. Internationally accepted liver enzyme thresholds for drug-induced liver injury were exceeded in 5 cases. In all cases, liver injury was classified as mixed hepatocellular and cholestatic. Infectious and other causes were excluded in each case. One patient with no pre-existing liver disease developed tender hepatomegaly and liver enzyme derangement exceeding 20 times the upper limit of normal following initiation of eculizumab. Recurrent liver injury following re-challenge with eculizumab necessitated its discontinuation and transition to plasma therapy. Hepatotoxicity in association with eculizumab is a potentially important yet previously unreported adverse event. We recommend monitoring liver enzymes in all patients receiving eculizumab. Further research is required to clarify the impact of this adverse event, to characterize the mechanism of potential hepatotoxicity, and to identify which patients are most at risk.
Targeted Oncology, 2014
The overexpression of membrane-bound complement regulatory proteins (mCRP; CD46, CD55, CD59) prev... more The overexpression of membrane-bound complement regulatory proteins (mCRP; CD46, CD55, CD59) preventing opsonization and complement-dependent cytotoxicity (CDC) is considered a major barrier for successful antibody-based cancer immunotherapy. To avoid a potential deleterious effect of mCRP neutralization on normal tissue cells, complement regulation has to be selectively targeted to the malignant cells. In this study, anti-mCRP small interfering RNAs (siRNAs) were encapsulated in transferrin-coupled lipoplexes for the specific delivery to transferrin receptor CD71(high) expressing BT474, DU145, and SW480 as well as corresponding CD71-knockdown (CD71(low)) tumor cells. Targeted delivery with transferrin-siRNA-lipoplexes became possible by charge neutralization and resulted in efficient silencing of all three mCRPs up to 90 %, which is dependent on their CD71 expression. The mCRP knockdown led to a significant increase of CDC on CD71(high) tumor cells by 68 % in BT474, 58 % in DU145, and 40 % in SW480 cells but only slightly increased on CD71(low) cells. Downregulation of CD46 and CD55 significantly increased C3 opsonization only on CD71(high) tumor cells. Our results demonstrate for the first time that by specific delivery of anti-mCRP siRNA through transferrin receptor, complement regulation can be selectively neutralized, allowing specific antibody-mediated killing of tumor cells without affecting healthy bystander cells, which appears to be a suited strategy to improve antibody-based cancer immunotherapy.
OncoImmunology, 2015
ABSTRACT Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by th... more ABSTRACT Complement-dependent cytotoxicity (CDC) is one of the effector mechanisms mediated by therapeutic anticancer monoclonal antibodies (mAbs). However, the efficacy of antibodies is limited by the resistance of malignant cells to complement attack, primarily due to the over-expression of one or more membrane complement regulatory proteins (mCRPs) CD46, CD55, and CD59. CD20-positive Burkitt lymphoma Raji cells and primary CLL cells are resistant to rituximab (RTX)-induced CDC whereas ofatumumab (OFA) proved to be more efficient in cell killing. Primary CLL cells but not CD52-positive acute lymphoblastic leukemia (ALL) REH cells were sensitive to alemtuzumab (ALM)-induced CDC. Upon combined inhibition on Raji and CLL cells by mCRPs-specific siRNAs or neutralizing antibodies, CDC induced by RTX and by OFA was augmented. Similarly, CDC of REH cells was enhanced after mCRPs were inhibited upon treatment with ALM. All mAbs induced C3 opsonization, which was significantly augmented upon blocking mCRPs. C3 opsonization led to enhanced cell-mediated cytotoxicity of leukemia cells exposed to PBLs or macrophages. Furthermore, opsonized CLL cells were efficiently phagocytized by macrophages. Our results provide conclusive evidence that inhibition of mCRPs expression sensitizes leukemic cells to complement attack thereby enhancing the therapeutic effect of mAbs targeting leukemic cells.
Molecular Immunology, 2010