ENHANCEMENT OF MITOGEN-INDUCED LYMPHOCYTE-PROLIFERATION IN SHEEP

Conditions were established to optimize the lymphocyte proliferation t est in sheep, a species where proliferation under standard conditions is lower than for other species. Optimum proliferation of phytohemaggl utinin-stimulated lymphocytes was achieved in TCM-199 supplemented wit h 5% (v/v) horse serum, 0.2 mM sodium pyruvate and 5 x 10(-5)M beta-me r captoethanol. Proliferative responses in this medium were 2.5-fold h igher or more than when using a standard medium (RPMI-1640 + 10% heat- inactivated fetal bovine serum). Lymphocytes cultured in medium contai ning horse serum also responded to concanavalin A as well as or better than lymphocytes cultured in medium with bovine serum. For both PHA a nd Con A, optimal incorporation of radioactivity was achieved when cel ls were pulsed with [H-3-methyl]-thymidine 72 h after addition of mito gen. The medium based on TCM-199 + horse serum could support interleuk in-2-induced proliferation. Furthermore, known inhibitors of lymphocyt e proliferation in sheep were effective in inhibiting lymphocytes cult ured in this medium.