Effect of in vivo exposure to allogeneic cells upon subsequent in vitro T cell responses and upon allograft rejection

The effect of intravenous injection of 10(6) BALB/c spleen cells into C57B1/6J recipients was assayed by both mixed lymphocyte culture (MLC) of recipient lymphocytes, and by grafting donor (BALB/c) thyroids into recipient mice. It was observed that a single intravenous injection produced depression of proliferative and cytotoxic T cell responses in MLC of spleen, lymph node and peripheral blood lymphocytes of the recipients. This effect was specific for the sensitizing genotype (MLC of recipient and third-party CBA/H lymphocytes was unaffected), and persisted for several days after sensitization. The pattern of this diminished response suggested that the effect was due to a combination of recruitment of reactive lymphocytes from peripheral lymphoid populations, and the generation of alloantigen (H-2?)-specific suppressor T cells in the spleen. In contrast to these findings in vitro, a similar sensitization led only to accelerated rejection of thyroid allografts in vivo.