Enhanced binding of low-affinity antibodies interacting simultaneously with targeted cell surface molecules and Fc receptor (original) (raw)

Characterization of Two Murine Monoclonal Antibodies Reactive with Human B Cells

Scandinavian Journal of Immunology, 1985

We describe two monoclonal antibodies, HH1 and HH2. Both reacted selectively with surface immunoglobulin (sIg)-positive human B cells. Both antibodies stained on average 7-8% of peripheral blood mononuclear cells. They have not been found to react with cells or cell lines of other haematopoietic cell lineages, except that HH2 was positive on a small percentage of cells of the erythroid cell line K562. The molecular weight of the HH1 antigen was 95 kD, as established by Western blotting. Neither of these two antibodies reacted with Ig determinants, Fc receptors, complement receptors, or known class-I or class-II molecules. A combination of these antibodies was used in a direct panning technique for high-yield enrichment of normal B lymphocytes from peripheral blood. The enriched B cells could be further purified by lysis of T cells (final yield, on average 72 +/- 8% of initial B cells) or by a second panning (yield, 35 +/- 11%). The purified B cells contained less than 1% contaminating T cells and less than 0.5% monocytes and were used in an assay for B-cell-stimulating factor which they showed a normal and very reproducible proliferative response.

A role for MHC Class II antigens in B-cell activation

Journal of Autoimmunity, 1989

anti-Class II antibodies. This proliferation was not epitope-restricted and was unaffected by low m.w. BCGF. Intracellular free calcium elevation was also examined as a marher of cellular activation. (Ca*+)i was increased after the binding and cross-llnlcing of an anti-DR antibody. The above results further support the role of Class II antigens as signal-transducing molecules. 215 0896-841 l/89/038215 f09 $03.00/O

Heterogeneity of immunoglobulin-associated molecules on human B cells identified by monoclonal antibodies

Proceedings of the National Academy of Sciences of the United States of America, 1992

Two covalently linked transmembrane molecules, encoded in mice by the mb-i and B29 genes, have been defined as integral components of the antibody receptor units expressed on B cells. We have produced monoclonal antibodies against an exposed extracellular epitope on the putative human equivalent of the mouse B29 product. These antibodies, CB3-1 and-2, were used to show that cytoplasmic expression of this molecule begs in human pro-B cells (terminal deoxynudeotidyltransferase-poitive, , chain-negative), whereas surface expression coincides strictly with surface immunolobulin expression ofall isotypes. Immunochemical analysis ofthe human immunoglobulin-associated molecules revealed greater molecular heterogeneity than has been noted for the murine analogues. This molecular heterogeneity of immunoglobulinassociated molecules varied as a function of differentiation stage and the immunoglobulin isotypes expressed by B-lineage cells. Our data support the hypothesis that biochemical heter

Hindrance of binding to class II major histocompatibility complex molecules by a single amino acid residue contiguous to a determinant leads to crypticity of the determinant as well as lack of response to the protein antigen

Proceedings of the National Academy of Sciences, 1995

The immune system has evolved the potential to respond to a wide variety of antigens, yet unresponsiveness to many foreign determinants is encountered frequently. Here, we report a lack of response to a particular determinant, hen egg lysozyme (HEL)-(46-61)-peptide (p46-61), in C57BL/6 (H-2b) mice, whereas a strong T-cell response to this determinant is obtained in major histocompatibility complex (MHC)-identical C3H.SW mice. However, (C3H.SW x C57BL/6)F1 mice respond weil to p46-61, suggesting the absence of a p46-61-specific "hole" in the T-cell repertoire in C57BL/6 mice. We further show that p46-61 cannot bind the I-Ab class II MHC molecule, whereas p46-60 lacking Arg1 exhibits good binding and is immunogenic in both strains. Thus, the presence ofthe hindering residue, Arg"L, renders p46-61, a dominant determinant in C3HLSW, into a silent, cryptic determinant in C57BL/6 mice.

Cellular mechanisms of antigen processing and the function of class I and II major histocompatibility complex molecules

Cell regulation, 1990

Antigen recognition: an overview Antigen recognition in humoral immunity has long been understood: the antigen-specific (Fab) portion of the antibody molecule binds directly to the antigen in its native state. The antibody molecules are found as antigen receptors on the plasma membrane of B cells and also as secreted proteins. In contrast, the biochemical basis for antigen recognition by T cells has only recently become clear. In general, T cells do not recognize antigens in their native conformation, but only after partial proteolysis within antigen processing or presenting cells (APC) into constituent peptides that bind to molecules encoded by genes in the major histocompatibility complex (MHC). The bimolecular complex of antigen peptide and MHC molecule is then displayed on the APC plasma membrane to be recognized by T-cell clones bearing a specific antigen receptor for it. This recognition leads to their stimulation and proliferation. The MHC molecules are, therefore, peptide carriers that serve to rescue peptides from extensive intracellular catabolism, making them available to the T-cell system (Unanue and Allen, 1987). They also constitute part of the antigenic determinant that T cells have evolved to recognize. Antigen presentation, therefore, includes a novel cell biological phenomenon: that a product from internal degradation of an exogenous protein becomes biologically active and recognized by another set of cells. Two classes of MHC molecules function in antigen presentation. The class I molecules (MHC-1) include HLA-A,-B, and-C in humans Review and H-2K, D, and L in mice. The class 11 molecules (MHC-11) include HLA-DP,-DQ, and-DR in humans and the I-A and l-E molecules in mice. This review will focus primarily on MHC-11 function, but it also discusses and compares the function of MHC-1 molecules. More extensive historical background is available in previous reviews (Unanue and Allen, 1987), whereas some recent advances are summarized elsewhere (Moller, 1987, 1988).

Antibodies to major histocompatibility complex class II inhibit proliferation, but increase production of soluble CD23 in lymphoblastoid B-cell lines

Immunology, 1993

Class II major histocompatibility complex (MHC) proteins bind and present peptide antigens to T cells. Moreover, their function as signal transduction molecules has recently been emphasized. Here we used Epstein-Barr virus (EBV)-transformed B-cell lines (B-LCL) in experiments to investigate the changes induced by binding of specific antibodies to HLA-DR molecules. Binding of the antibodies induced, in an allele-specific manner, striking non-cytotoxic inhibition of B-LCL proliferation. This inhibition was associated with an increase in shedding of soluble CD23. These findings provide further evidence for the function of MHC class II proteins as signal transduction molecules which may be important in B-cell activation.