Loss with age in NZB/W mice of thymic suppressor cells in the graft vs host reaction

The ability of lymphoid cells from NZB/W female mice to induce graft versus host disease (GVH) was studied by injections into newborn C3H/HeJ mice followed 9 days later by the Simonsen spleen weight:body weight assay. Spleen cells, 5 x 10⁶, led to increasing GVH with increasing age until about 5 months of age, after which a decline in GVH was observed. The heightened responsiveness of 4.5 month or 6 month NZB/W spleen cells could be suppressed by syngeneic lymphoid cells from mice under 2 months of age but not from mice 12 months of age. This suppressive function of young thymocytes and spleen cells increased with increasing cell dose. The suppressive function gradually decreased in thymocyte populations between 1 and 4 months of age. Nevertheless, 4 month thymocytes that no longer demonstrated suppressor function were able to synergize with 12 month spleen cells. These studies suggest that suppressor cells are lost as NZB/W mice age and that suppressor function is lost before helper function.