Antibacterial activity of bovine mammary gland lymphocytes following treatment with interleukin-2.

The antibacterial characteristics of bovine mammary gland lymphocytes were evaluated following in vitro activation with recombinant human interleukin-2. Mammary gland effector cell populations were prepared by enzymatic digestion of mammary tissue followed by centrifugation through a discontinuous Percoll gradient. Functional activity of cells cultured for 48 h with or without interleukin-2 were evaluated by direct cytotoxicity using K562 target cells and by antibacterial activity against Staphylococcus aureus. Cytotoxic activity of interleukin-2-treated mammary gland lymphocytes was enhanced compared with control cultures, which exhibited no cytotoxic capabilities following 48 h of culture. Bactericidal activity also was elevated in cells cultured in interleukin-2-supplemented media. Enhanced expression of major histocompatability complex class II molecules on the surface of interleukin-2-treated lymphocytes was associated with the higher level of cell activation. Phenotypic analyses of the recovered population showed that the majority of cells were lymphocytes bearing CD2 molecules. It may be possible to activate these effector cell populations in vivo and increase resistance of the mammary gland to bacterial infections in a nonspecific manner.