Synergy among lymphoid cells mediating the graft-versus-host response. V. Derivation by migration in lethally irradiated recipients of two interacting subpopulations of thymus-derived cells from normal spleen.

Spleen cells from normal adult mice were injected into lethally irradiated adult syngeneic recipients. 24 h later, cell suspensions were prepared from the recipients' spleens or peripheral lymph nodes and tested either alone or combined for their capacity to elicit graft-versus-host (GVH) reactions in neonatal F(1) recipients, using the Simonsen spleen weight assay. Either the lymph node-seeking subpopulation or the spleen-seeking subpopulation alone was markedly deficient in its ability to provide a GVH reaction when compared with the normal population from which it was derived. However, an appropriate mixture of the two had a reactivity characteristic of the parent population. Both subpopulations were sensitive to treatment with anti-theta antibody and complement in vitro. These results provide a convincing demonstration of the functional heterogeneity within the pool of thymus-derived cells present in a single normal lymphoid tissue. They strongly suggest that the normal expression of GVH reactivity of such a tissue involves an interaction among distinct subpopulations of thymus-derived cells.