Suppression of sheep and goat lymphocyte proliferation by sheep, goat, and sheep x goat hybrid trophoblast tissue cultures.

: Immunosuppressive activity of conditioned medium from cultured ovine, caprine, and hybrid trophoblast tissue was examined. Conceptuses were obtained from naturally mated donor ewes and does at d 20 of gestation and trophoblast tissue was cultured for 24 h in medium supplemented with 15% calf serum and 1% antibiotic/antimycotic. Conditioned medium was added to pokeweed mitogen-stimulated sheep and goat lymphocyte cultures. Quantification of [3H]thymidine uptake by cells was used to measure lymphocyte proliferation. Ovine, caprine, and hybrid conditioned medium effectively suppressed sheep and goat lymphocyte proliferation (P less than .01). There were no differences (P greater than .05) between the immunosuppressive activity of the three tissue types on either sheep or goat lymphocytes. For all treatment groups, sheep lymphocytes were suppressed more than goat lymphocytes (P less than .05). These results indicate that, at d 20 of gestation, sheep x goat hybrid trophoblast tissue is capable of suppressing pokeweed mitogen-stimulated lymphocyte proliferation.