SUMMARY Hyporesponsiveness to a universe of bacterial and dietary antigens from the gut lumen is a hallmark of the intestinal immune system. Since hyperresponsiveness against these antigens might be associated with inflammation, we studied the immune response to the indigenous intestinal microflora in peripheral blood, inflamed and non‐inflamed human intestine. Lamina propria monocuclear cells (LPMC) isolated from inflamed intestine but not peripheral blood mononuclear cells (PBMC) of IBD patients with active inflammatory disease strongly proliferated after co‐culture with sonicates of bacteria from autologous intestine (BsA), Proliferation was inhibitable by anti‐MHC class II MoAb, suggesting that it was driven by antigen, LPMC from adjacent non‐inflamed intestinal areas of the same IBD patients and PBMC or LPMC isolated from non‐inflamed intestine of controls and patients with IBD in remission, in contrast, did not proliferate, PBMC or LPMC which had been tolerant to bacteria from autologous intestine, however, strongly proliferated after co‐culture with bacterial sonicates from heterologous intestine (BsH). This proliferation was associated with an expansion of CD8+ T cells, increased expression of activation markers on both CD4+ and CD8+ lymphocyte subsets, and production of IL‐12, interferon‐gamma (IFN‐γ), and IL‐10 protein. These results show that tolerance selectively exists to intestinal flora from autologous but not heterologous intestine, and that tolerance is broken in intestinal inflammation. This may be an important mechanism for the perpetuation of chronic IBD.

Objective. MRL-FasConclusion. Taken together, our findings suggest that IL-18-producing TECs may directly be involved in the pathogenesis of lupus nephritis.

The expression of intercellular adhesion molecule-I (ICAM-1, CD54)

Monoclonal antibodies were raised against homogeneous Ro and La antigens, two proteins associated with Ro and La ribonucleoproteins (RNPs). The specificity of the monoclonal antibodies was proven by immunoblot analysis and by immunoprecipitation. The anti-Ro antibody reacted with a Mr 95,000 protein in a mouse lymphoma cell extract and with a Mr 60,000 polypeptide in extracts from human spleen. The anti-La antibody recognized a Mr 50,000 polypeptide in the mouse L5178y cell extract. (3,4). RNA analysis revealed that Ro small cytoplasmic RNPs (scRNPs) carry the La as well as the Ro determinants and, consequently, were a subclass of La RNPs (5). Based on immunoprecipitation studies, the molecular weight of the Ro antigen(s) was determined to be 94,000 (90,000) (6), while analysis by immunoblotting revealed a Mr of 57,000 (7). Comparative experiments using the techniques of counterimmunoelectrophoresis and immunoblotting led to the assumption that the Ro antigenic determinant is labile when exposed to NaDodSO4 (8 (Junction City, OR).Preparation of the Anti-Ro and Anti-La mAbs. Homogeneous Ro and La antigens were prepared from L5178y mouse lymphoma cells (38). Briefly, crude cell extracts were enriched for Ro and La antigens by ammonium sulfate fractionation (45-80% saturation), ribonuclease A treatment, and Sephadex G-150 gel filtration. This extract was further purified by immunoaffinity column chromatography with monospecific antibodies against the Ro and La antigens according to the procedure described below for the application of mAbs. The antisera were obtained from patients with autoimmune disorders. The homogeneity of the antigen preparations was proven by NaDodSO4/gel electrophoresis, and their specificities, by immunoblotting (12) with standardized reference antisera (anti-Ro and anti-La; Centers for Disease Control, Atlanta). General procedures for preparation of mAbs (12,13)

Humoral and cellular immune reactions to heat-shock proteins have been implicated in the pathogenesis of arthritis. Heat-shock proteins occur in bacteria as well as all eukaryotes and have been highly conserved during evolution. Cross-reactivity between bacterial and human heat-shock proteins induced at the site of inflammation may underlie the pathogenesis of some forms of arthritis. In order to test this hypothesis, we raised and cloned a Yersinia-specific T cell line from the synovial fluid lymphocytes of a patient with Yersinia-induced reactive arthritis. From this line we obtained a CD4+ T cell clone that proliferated in response to Yersinia antigens and both to the mycobacterial and the human 65-kDa heat-shock protein. This T cell clone also proliferated in response to autologous heat-stressed antigen-presenting cells as well as to synovial fluid mononuclear cells from the inflamed joint, thus showing true autoreactivity against endogenously synthetized self-antigen. These results demonstrate the induction of an autoimmune T cell response by a natural bacterial infection and support the important role of heat-shock proteins in the pathogenesis of immune-mediated arthritis.