The TcR‐CD3 Complex is Required for Activation of Human Lymphocytes with Staphylococcal Enterotoxin A

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Abstract
The involvement of the T-cell receptor (TcR)-CD3 complex in activation of human mononuclear cells by staphylococcal enterotoxin A (SEA) was investigated. TcR-CD3 molecular complex expression was modulated with monoclonal anti-CD3 antibodies. The proliferative response of such modulated cells to optimal doses of phytohaemagglutinin and monoclonal anti-CD3 antibodies and to suboptimal doses of SEA was greatly impaired. In concentrations above 1 ng/ml, SEA could also activate the modulated cells to a certain extent, apparently due to re-expression of low levels of SEA-activated cells to produce interleukin 2 and gamma interferon. Analysis of cloned cells revealed that SEA could only activate CD3+ but not CD3- clones. Both CD4+ and CD8+ clones were activated. The results show that SEA activates human T cells by a mechanism involving the TcR-CD3 molecular complex.