Most CD8(+) T cells in cultures of bovine mononuclear cells stimulated with
staphylococcal enterotoxin C1 develop an unusual phenotype characterized b
y expression of activation molecule 3 (ACT3). This superantigen-dependent p
henotype may be relevant to immunopathogenesis mediated by certain microbia
l toxins. The size and N-terminal sequence of immunoprecipitated ACT3 indic
ate that ACT3 is the bovine orthologue of CD26.