Functional capacities of chick embryo thymocytes in the mixed lymphocyte reaction

Thymocytes from chick embryos homozygous for the B19 haplotype of the major histocompatibility locus were tested in a one way MLR either as responder or stimulator cells, against adult peripheral blood lymphocytes from B14/14 or B19/19 strains. 13-day embryonic thymocytes were strongly stimulated by adult allogeneic PBL. By contrast 16-day thymocytes were unresponsive. This difference might be related to the rhythmic waves of stem cell entry and multiplication which characterize the ontogeny of the avian thymus. Mitomycin-treated thymocytes from 13-day or 16-day embryos were both efficient in stimulating thymidine uptake by adult allogeneic PBL.