MODULATION OF BOVINE MONONUCLEAR CELL-PROLIFERATION DURING PHYSIOLOGICAL TRANSITIONS OF THE MAMMARY-GLAND

Mammary secretions and blood were collected from five primiparous Holstein cows 14 d following cessation of milking and 14 d prior to parturition for preparation of serum and mammary secretion skim fractions. Mammary secretions and blood were collected from the same animals 15 to 18 d following cessation of milking and 2 to 13 d prior to parturition for isolation of mononuclear cells. Effects of serum on mammary gland mononuclear cell proliferation and skim fractions from mammary secretions on blood mononuclear cell proliferation were evalated. Mononuclear cell proliferation was evaluated in a mitogen-induced lymphocyte proliferation assay and in a mixed leukocyte assay. Proliferative responses of blood and mammary gland mononuclear cells did not vary significantly between the two time periods evaluated. Mammary secretion skim fractions obtained at both time periods significantly suppressed blood mononuclear cell proliferation. In contrast, exogenous serum enhanced mammary gland mononuclear cell proliferation in response to mitogens and allogeneic cells. Ability to enhance in vitro proliferation of mammary mononuclear cells isolated during physiological transitions of the mammary gland may suggest the potential for enhancing mammary mononuclear cell proliferation in vivo to reduce incidence of new intramammary infections at times when the mammary gland is highly susceptible.