[The analysis of the immune response to Streptococcus mutans cell wall antigen and allo-MHC antigens in the rat].

RT1 is the major histocompatibility complex (MHC) of the rat, which is equivalent to H-2 of mice and HLA of human. In the present study, the role of RT1, especially class II antigens (RT1-B/D antigens) in the immune response to Streptococcus mutans cell wall antigen (SMA) and allo-MHC antigens was investigated. The results are as follows. 1) Eleven strains of inbred rats were divided into high or low responders with respect to their immune responsiveness to SMA. 2) Having examined the immune responsiveness to SMA of RT1-congenic strains, it is shown that there is a correlation between the immune responsiveness and RT1 haplotypes. 3) The low responsiveness to SMA of LEW rats was mostly mediated by MRC-OX8+ suppressor T cells. 4) By the inhibition test of allo-MLR (mixed lymphocyte reaction) with monoclonal antibodies, HOK7 HOK12 and HOK33, it has been shown that RT1-B/D antigens are MLR-stimulatory molecules and that Ia+ antigen presenting cells (APC) of responder cells are necessary in the recognition of allo-MHC antigens. 5) It is suggested that there are two recognition pathways of allo-MLR. In one of them, allo-MHC antigens are directly recognized by responder T cells, in another, they are recognized by responder T cells with help of Ia+ APC.