The Mitogenic Effects of Staphylococcus Aureus Toxins on Bovine and Porcine Peripherial Blood Lymphocytes

The hypothesis that Staphylococcus enterotoxin type A (SEA) and Staphylococcus enterotoxin type B (SEB) could induce mitogenisis in bovine and porcine peripheral blood lymphocytes (PBLs) was tested. This is one of the first studies to demonstrate the immunological effects of SEA and SEB with bovine and porcine lymphocytes. Previous studies using human and murine PBLs (Vroegop and Buxser, 1989; Marrack and Kappler, 1990) were consistent with the reported results. A two-fold dilution series of these enterotoxins was used to determine the range of mitogenic concentrations with bovine and porcine PBLs. The results indicated that SEA induced peak proliferation at 0.05 µg / ml and 0.01 µg / ml with the bovine and porcine PBLs, respectively. However, with bovine PBLs, SEB induced two peaks of maximum proliferation at concentrations of 0.1 µg / ml and 5.0 µg / ml, and a peak of 5.0 µg / ml with porcine PBLs. Polyclonal antisera to SEA and SEB were used to inhibit the observed proliferation, and demonstrated that the mitogenisis was due to the enterotoxins and not due to other microbial products. The results showed a complex pattern and cross-reactivity between the polyclonal antisera, Con A and the enterotoxins. Anti-SEA antibodies inhibited SEA induced proliferation better than anti-SEB antibodies with lymphocytes from both species of animals. Anti-SEB antibodies inhibited SEB induced proliferation better than anti-SEA antibodies in both species. Both antisera inhibited the Con A response significantly in cattle. A final set of assays examined the ability of SEA and SEB to induce immunosuppressive activity. Pretreatment of the PBLs with SEA and SEB resulted in suppression of lymphocyte proliferation in a threshold manner with the bovine PBLs. While, pretreatment of the PBLs with SEA resulted in suppression of lympocyte proliferation in a ratio dependent manner with procine PBLs. This data was consistent with previously reported results that indicated SEA and SEB induced anergy or activation-induced cell death (Yuh et al., 1993; Gonzalo et al., 1994) or activated a population of suppressor lymphocytes (Platsoucas et al., 1986; Donnely and Roger, 1982)