Third, it remains possible that EtxB-receptor conversation may have other effects on the activity of antigen-presenting cells, for example, modulating uptake and processing or the expression of important costimulatory molecules
Third, it remains possible that EtxB-receptor conversation may have other effects on the activity of antigen-presenting cells, for example, modulating uptake and processing or the expression of important costimulatory molecules. glycolipids and galactoproteins. The importance of receptor conversation in mediating protection from arthritis was demonstrated by the failure of a non-receptor-binding mutant of EtxB to elicit any protective effect. Analysis of T cell responses to collagen, in cultures of draining lymph node cells, revealed that protection was associated with a marked increase in interleukin 4 production concomitant with a reduction in interferon levels. Furthermore, in guarded mice there was a significant reduction in anti-collagen antibody levels as well as an increase in the IgG1/IgG2a ratio. These observations show that protection is usually associated with a shift in the Th1/Th2 balance as well as a general reduction in the extent of the anti-type II collagen immune response. This suggests that EtxB-receptor-mediated modulation of lymphocyte responses provides a means of preventing MP-A08 autoimmune disease. Autoimmune diseases remain a major health problem despite enormous efforts to understand the underlying causative mechanisms. The lack of clarity with regard to both the predisposing factors and the precise antigenic targets of the immune response have restricted the development of effective therapeutic approaches. However, recent evidence suggests that brokers which modulate the nature of the immune response may be effective as a means of prophylaxis or treatment. We recently reported that this nontoxic B subunit of heat-labile enterotoxin (EtxB) exerts profound modulatory effects on lymphocyte populations administration of monoclonal antibodies to CD4, TCR, or class II major histocompatibility complex (MHC; refs. 15C17). Evidence suggests that the nature of the CD4+ T cell response with respect to the balance between Th1 cytokines [interferon (IFN-) and interleukin (IL)-2] and Th2 cytokines (IL-4, IL-10, and IL-13) plays an important role in CIA. As with other inflammatory autoimmune diseases, CIA appears to be promoted by a Th1-dominated MP-A08 response and is down-regulated if relative levels of Th2 cytokines are increased. Thus, early injection of IL-12 (a cytokine that enhances Th1 responses) or IFN- increases the severity of arthritis in collagen-challenged mice (18, 19), whereas treatment with IL-4, IL-13, or IL-10 prevents disease (20, 21). In addition, time course studies have shown that IFN–producing T cells dominate the anti-CII response during disease onset but that later remission is accompanied by a decline in IFN- levels and increased IL-10 (22). Although the precise role of Th1 cytokines in the causation of CIA remains unclear, the ability of IFN- to promote the production of complement fixing IgG2a antibody and the ability to MP-A08 enhance macrophage activation and inflammatory mediator release are likely to be crucial (23). In this paper, we demonstrate that receptor binding by EtxB can prevent autoimmune disease in the DBA/1 mouse model of arthritis. Disease protection was evident both clinically and histologically when EtxB was given either at the same time or 21 days after collagen challenge. EtxB did not abrogate the induction of the anti-CII immune response; however, the profiles of T cell cytokines and antibody isotypes was substantially altered. These studies identify EtxB-receptor conversation as an important target for modulating adverse immune reactions and are suggestive of a role for GM1-mediated signaling events in controlling cells of the immune system. MATERIALS AND METHODS Mice. Male DBA/1 mice MP-A08 were purchased from Harlan Olac (Bicester, U.K.) and maintained in the departmental animal facilities. Mice were 10 weeks of age at the time of immunization. Antigens, Immunization, and Induction of Arthritis. Recombinant preparations of EtxB and EtxB(G33D) were purified as reported (24). Both proteins are well characterized with respect to purity, physicochemical properties, and their ability to bind to GM1 (1). Either protein (100 g) was injected s.c. into the dorsal flank in incomplete Freunds Rabbit Polyclonal to LDLRAD3 adjuvant (IFA). CII collagen (from bovine nasal septum; Sigma) was dissolved in 0.05 M acetic acid. To induce arthritis, 100 g of CII was injected s.c. at the base of the tail in complete Freunds adjuvant (CFA) and in IFA 21 days later. For use in T cell assays, samples of CII were placed in boiling water for 40 min before extensive dialysis against Hanks balanced salt answer (Ca2+ and Mg2+ free; Flow Laboratories) and sterilization by filtration (0.2-m.