REGULATION OF LEUKOCYTE INTERLEUKIN-2 AND INTERLEUKIN-2 RECEPTOR GENE-EXPRESSION BY RABBIT BLASTOCOELIC FLUID

The mechanisms underlying the inhibition of lymphocyte proliferative r esponse by rabbit blastocoelic fluid collected on day 12 of embryonic development were investigated. Treatment with blastocoelic fluid, even in the presence of concanavalin A, maintains lymphocytes in a quiesce nt state by preventing cell entry into the S phase of the cell cycle. Gene expression of interleukin 2 receptor is completely blocked by tre atment with blastocoelic fluid as are the secretion and gene expressio n of interleukin 2. Addition of interleukin 2 to prestimulated interle ukin 2 receptor positive lymphocytes failed to downregulate the expres sion of high-affinity interleukin 2 receptor and completely abolished the embryonic fluid-mediated inhibitory effect on [H-3]thymidine incor poration. Taken together, these results suggest that embryonic fluid h as differential inhibitory effects, depending on the activation state of the lymphocytes. Nevertheless, inhibition of interleukin 2 and inte rleukin 2 receptor expression by embryonic fluid restrains immune cell activity and therefore can be implicated in the survival of the fetal semi-allograft.