Immunomodulating activities of staphylococcal enterotoxins. I. Effects on in vivo antibody responses and contact sensitivity reaction.

The immunomodulating effects of staphylococcal enterotoxins on in vivo immune responses in C57BL/6 mice were examined. Of the five serological types A (SEA), B, C, D, and E (SEE), only SEA and SEE markedly suppressed the antibody response to sheep red blood cells (SRBC) when injected 1 day before or on the day of immunization with SRBC. Further study of SEA revealed that it did not affect the antibody response to a thymus-independent antigen, salmonella flagella, but did affect the T-cell-mediated immune response. Contact sensitivity to dinitrofluorobenzene (DNFB) was suppressed when SEA was injected before sensitization or before challenge with DNFB, indicating that SEA affected both the afferent and efferent phases of DNFB contact sensitivity. As the suppression of DNFB contact sensitivity could be transferred by anti-Thy-1.2 antibody-sensitive spleen cells of SEA injected donors into normal or DNFB-sensitized recipients, the suppression was thought to be an active one. However, SEA could augment the DNFB contact sensitivity when injected on the third day after sensitization with DNFB. These results indicate that the immunomodulating effects of SEA can be mediated by the T-cell function.