A series of experiments were carried out to further characterize the previously discovered Heligmosomoides polygyrus, adult worm homogenate (AWH), superantigen. AWH, in contrast to staphylococcal enterotoxin B (SEB) superantigen, was totally unable to stimulate naive thymocytes, in either the presence or the absence of exogenous accessory cells (AC). Experiments using AC from B10 congenic mice failed to indicate a requirement for a specific MHC haplotype for successful presentation of the AWH superantigen and also indicated that the presence or absence of the H-2, E molecule on AC did not affect AWH stimulation of T cell hybridamos. Furthermore, AWH was found to require the presence of MHC Class I-positive AC in order to stimulate T cell hybridomas, while, in contrast, the absence of MHC Class II on AC did not affect the superantigenic properties of AWH. Initial characterization of the T cell hybridomas stimulated by the AWH superantigen, indicated that all were CD4-positive and that three of them expressed TCR Vβ8.1. Hence AWH superantigen can stimulate TCR Vβ8.1/CD4-positive T cells only in the presence of MHC Class I-positive AC.
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