STAPHYLOCOCCAL ENTEROTOXIN B STIMULATION OF BALB/c LYMPHOCYTE MITOGENESIS AND POTENTIAL RELATIONSHIP TO THE Mls RESPONSE

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Abstract
Staphylococcal enterotoxin B (SEB) is a T cell mitogen with properties different from the plant lectin mitogens. We examined the stimulation of mitogenesis induced by SEB in BALB/c mouse spleen cells and its relationship to major histocompatibility complex (MHC) and related cell surface proteins. Based on the ability of specific monoclonal antibodies to block mitogenesis, SEB stimulation appears to be more dependent on interaction with I-E than with I-A class II MHC molecules. Additionally, anti-L3T4, and possibly other antibodies specific for proteins related to the T cell receptor complex, were inhibitory. When A20 cells were treated with SEB and used to stimulate BALB/c spleen cells which were not otherwise exposed to SEB, the treated A20 cells were capable of stimulating mitogenesis of the BALB/c spleen cells. The data support the hypothesis that SEB stimulation is mediated primarily by interactions with class II MHC proteins and possibly proteins in the T cell receptor complex. We also observed that the presence of SEB in DBA/2 (Mlsa)-stimulated BALB/c (Mlsb) spleen cell cultures enhanced the BALB/c mitogenesis three-fold over the sum of the SEB-plus Mls-stimulated mitogenesis. These results suggest that SEB may be a useful tool for further exploration of the Mls response.