T cell specificity and cross reactivity towards enterobacteria, bacteroides, bifidobacterium, and antigens from resident intestinal flora in humans

Abstract

Background: T cell responses to normal intestinal bacteria or their products may be important in the immunopathogenesis of chronic enterocolitis.

Aims: To investigate the T cell specificity and cross reactivity towards intestinal bacteria.

Patients/methods: T cell clones were isolated with phytohaemagglutinin from peripheral blood and biopsy specimens of inflamed and non-inflamed colon from five patients with inflammatory bowel disease (IBD) and two controls. T cell clones were restimulated with anaerobic Bacteroides and Bifidobacteria species, enterobacteria, and direct isolates of aerobic intestinal flora. T cell phenotype was analysed by single-cell immunocyte assay.

Results: Analysis of 96 T cell clones isolated from peripheral blood and biopsy specimens from two patients with IBD showed that both Bifidobacterium and Bacteroides species specifically stimulate proliferation of CD4+TCRalphabeta+ T cell clones from both sites and that cross reactivity exists between these anaerobic bacteria and different enterobacteria. Analysis of 210 T cell clones isolated from three patients with IBD and two controls showed that indigenous aerobic flora specifically stimulate T cell clones from peripheral blood and biopsy specimens from a foreign subject. Some of these flora specific T cell clones were cross reactive with defined enterobacteria. In addition, T cell clones stimulated by their own indigenous aerobic flora were identified in patients with IBD.

Conclusion: Immune responses to antigens from the intestinal microflora involve a complex network of T cell specificities.

Figure 1

Clonal T cell responses towards Bacteroides and Bifidobacterium. T cell clones were isolated, using phytohaemagglutinin (PHA), from two patients with ulcerative colitis (patient R: peripheral blood n = 14, non-involved colon n = 12, involved colon n = 18; patient B: peripheral blood n = 12, non-involved colon n = 17, involved colon n = 23) and restimulated with the indicated antigens for 42 hours. Mean proliferation of T cell clones from peripheral blood (RP3), non-involved colon (RB−9 and BB−17), and involved colon (RB+2, RB+16, BB+6, and BB+22) stimulated by Bacteriodes thetaiotaomicron (ATCC 12290) or Bifidobacterium bifidum (ATCC 35914) is shown as measured by [³H]thymidine incorporation in triplicate cultures. Clone BP6 is representative of other T cell clones reactive with enterobacteria only. All T cell clones were CD4+TCRαβ+ by single-cell immunocyte assay.

Figure 2

Clonal T cell responses to aerobic intestinal flora. T cell clones were isolated with phytohaemagglutinin (PHA) from two controls (patient A, bile acid induced diarrhoea: peripheral blood n = 23, colon n = 15; patient W, irritable bowel syndrome: peripheral blood n = 20, colon n = 19) and restimulated with the indicated antigens for 42 hours. Aerobic intestinal flora was obtained from intestinal biopsy specimens touched to blood agar plates and grown under aerobic conditions. Sonicates from outgrowing bacteria were used as BsA (sonicates and mononuclear cells from the same person) or BsH (sonicates and mononuclear cells from different people). Mean proliferation of T cell clones from peripheral blood (WP2 and WP18) and colon (AB−3, WB−5, and WB−15) stimulated by BsA or BsH is shown as measured by [³H]thymidine incorporation of triplicate cultures. All T cell clones were CD4+TCRαβ+ by single-cell immunocyte assay. Incubation of antigen presenting cells with the indicated stimuli without T cell clones resulted in <500 cpm.