Influence of Recombinant Bovine Somatotropin (Sometribove) on Mononuclear Cells During the Nonlactating Period

Recombinant bST was evaluated as a potential immunoenhancer of bovine peripheral blood and mammary gland mononuclear cells during the nonlactating period. Cows (n = 4 per group) were assigned to one of four treatments: 1) untreated, 2) treated with recombinant bST during lactation only, 3) treated with recombinant bST during the nonlactating period only, and 4) treated with recombinant bST during lactation and the nonlactating period. Recombinant bST treatment during the nonlactating period had no effect on proliferation of bovine blood or mammary gland mononuclear cells in response to stimulation by mitogens or allogeneic cells. Recombinant bST treatment during the nonlactating period enhanced interleukin-2 secretion by mononuclear cells isolated from cows treated also with recombinant bST during lactation. However, recombinant bST treatment during the nonlactating period had little effect on interleukin-2 secretion by mononuclear cells from cows not treated with recombinant bST during lactation. Results of this study suggest that recombinant bST alters effector functions rather than proliferation of bovine mononuclear cells.