Segmented filamentous bacteria are potent stimuli of a physiologically normal state of the murine gut mucosal immune system - PubMed (original) (raw)

Segmented filamentous bacteria are potent stimuli of a physiologically normal state of the murine gut mucosal immune system

G L Talham et al. Infect Immun. 1999 Apr.

Abstract

Segmented filamentous bacteria (SFB) are autochthonous bacteria inhabiting the intestinal tracts of many species, including humans. We studied the effect of SFB on the mucosal immune system by monoassociating formerly germfree C3H/HeN mice with SFB. At various time points during 190 days of colonization, fragment cultures of small intestine and Peyer's patches (PP) were analyzed for total immunoglobulin A (IgA) and SFB-specific IgA production. Also, phenotypic changes indicating germinal center reactions (GCRs) and the activation of CD4(+) T cells in PP were determined by using fluorescence-activated cell sorter analyses. A second group of SFB-monoassociated mice was colonized with a gram-negative commensal, Morganella morganii, to determine if the mucosal immune system was again stimulated and to evaluate the effect of prior colonization with SFB on the ability of M. morganii to translocate to the spleen and mesenteric lymph nodes. We found that SFB stimulated GCRs in PP from day 6 after monoassociation, that GCRs only gradually waned over the entire length of colonization, that natural IgA production was increased to levels 24 to 63% of that of conventionally reared mice, and that SFB-specific IgA was produced but accounted for less than 1.4% of total IgA. Also, the proportion of CD4(+), CD45RBlow T cells, indicative of activated cells, gradually increased in the PP to the level found in conventionally reared mice. Secondary colonization with M. morganii was able to stimulate GCRs anew, leading to a specific IgA antibody response. Previous stimulation of mucosal immunity by SFB did not prevent the translocation of M. morganii in the double-colonized mice. Our findings generally indicate that SFB are one of the single most potent microbial stimuli of the gut mucosal immune system.

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Figures

FIG. 1

FIG. 1

In order to assess the progress of germinal center reactions and activation of T cells in PP, cell suspensions from PP of three to five mice were analyzed by FACS analysis at various times following the colonization of formerly GF mice with SFB. These analyses were compared to those of PP from GF and conventionally reared (CNV) mice. Cells were stained with a germinal center marker, PNA, conjugated to FLU or FLU-labeled goat anti-mouse IgA, respectively, and then both were counterstained with PE-conjugated anti-kappa chain to monitor the development of germinal center reactions. Cells were also stained with the CD4 T-cell activation marker CD45RB, conjugated to FLU and counterstained with PE-conjugated anti-CD4 to monitor T-cell activation.

FIG. 2

FIG. 2

Production of total IgA in supernatant of organ fragment cultures of PP and small intestine of GF, conventionally reared (CONV), and SFB-monoassociated C3H/HeN mice at various time points. RIA was used to detect IgA. Data are means ± standard errors of the mean. SI, small intestine; D, duodenum; J, jejunum; I, ileum. The number of fragment cultures per tissue per time point ranged from 4 to 14.

FIG. 3

FIG. 3

Production of total IgA in supernatant of organ fragment cultures of PP and small intestine (SI) of GF mice, conventionally reared (CNV) C3H/HeN mice, and C3H/HeN mice that had been monoassociated with SFB and then double associated (at day 113) with M. morganii. RIA was used to detect IgA. Data are means ± standard errors of the mean. The number of fragment cultures per tissue per time point ranged from 6 to 19.

FIG. 4

FIG. 4

Production of anti-SFB specific IgA in supernatant of organ fragment cultures of PP and small intestine of GF, conventionally reared (CONV), and SFB-monoassociated C3H/HeN mice at various time points. RIA was used to detect IgA. Data are means ± standard errors of the mean. SI, small intestine; D, duodenum; J, jejunum; I, ileum. The number of fragment cultures per tissue per time point ranged from 4 to 14.

FIG. 5

FIG. 5

Production of anti-SFB specific IgA in supernatant of organ fragment cultures of PP and small intestine (SI) of GF mice, conventionally reared (CNV) C3H/HeN mice, and C3H/HeN mice that had been monoassociated with SFB and then double associated (at day 113) with M. morganii. RIA was used to detect IgA. Data are means ± standard errors of the mean. The number of fragment cultures per tissue per time point ranged from 6 to 19.

FIG. 6

FIG. 6

Production of anti-M. morganii specific IgA in supernatant of organ fragment cultures of PP and small intestine (SI) of GF mice, conventionally reared C3H/HeN mice, and C3H/HeN mice that had been monoassociated with SFB and then double associated (at day 113) with M. morganii. RIA was used to detect IgA. Data are means ± standard errors of the mean. Four fragment cultures were done per tissue per time point.

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