PROLIFERATIVE RESPONSE AND CYTOKINE PRODUCTION OF BOVINE PERIPHERAL-BLOOD MONONUCLEAR-CELLS INDUCED BY THE SUPERANTIGENS STAPHYLOCOCCAL ENTEROTOXINS AND TOXIC SHOCK SYNDROME TOXIN-1

The potential of staphylococcal enterotoxin A (SEA), B (SEE), C (SEC) and toxic shock syndrome toxin-l (TSST-1) to act as superantigens by i nducing polyclonal T-cell mitogenesis and cytokine production was test ed on bovine peripheral blood mononuclear cells (PBMC). These four tox ins were capable of inducing strong proliferative response of PBMC fro m carves over a broad dosage range (1 pg/ml to 1 mu g/ml) in vitro. Th e toxin-activated blast cells consisted of both CD4(+) T-cells and CD8 (+) T-cells, but the T-cell proliferation depended upon the presence o f monocytes. Treatment of monocytes with monoclonal antibody to major histocompatibility complex class II antigens substantially inhibited t he toxin-induced T-cell proliferative response, but paraformaldehyde-f ixation did not abrogate the accessory function. SEA, SEE, SEC and TSS T-1, all induced the in vitro release of interleukin-2, interferon gam ma and tumor necrosis factor cu in a dose dependent manner. The result s indicate that SEA, SEE, SEC and TSST-1 are capable of acting as supe rantigens by stimulating bovine T-cells as shown in the human and muri ne systems. The possible implications of these toxins in the immunopat hogenesis of bovine mastitis caused by the infection with Staphylococc us aureus are discussed.