Mitogenicity of formalinized toxoids of staphylococcal enterotoxin B

Staphylococcal enterotoxin B is a potent mitogen for mouse and human lymphocytes. Mitogenic activity was retained after detoxification of the enterotoxin by formaldehyde at pH 5.0, 7.5, OR 9.5. The most active toxoid (pH 7.5) was separated into a monomeric, a dimeric, and a polymeric fraction (1 x 10(5) to 3 x 10(5) molecular weight) by gel filtration, and although each fraction demonstrated mitogenic activity, the polymeric fraction was clearly the most efficacious. These data show that mitogenicity of staphylococcal enterotoxin B does not depend on toxicity. This suggests that the mitogenic and toxic activities are effected by different sites on the molecule.