Time dependence of the effect of splenectomy on graft-versus-host reactivity of lymph node cells

Changes in cell-mediated reactivity of lymph node cells at various intervals after splenectomy were investigated in three assays measuring the GVH reactivity of parental cells in F1 hybrids --splenomegaly test in very young recipients and popliteal lymph node enlargement assay in adults measuring the proliferative component of the reaction, and mortality assay in sublethally irradiated recipients measuring the killer activity of the cell inoculum. During the early postsplenectomy period the reactivity of the particular amounts of lymph node cells was lower than that of cells from normal donors, but at about 3 weeks after splenectomy it was higher. The increase was of short duration in the proliferation assay and at 5 weeks the reactivity declined markedly below the control values. The increase in activity persisted for 5 weeks after splenectomy in the "killer" assay. It is probable that the described changes in cell-mediated reactivity are involved in the total effect of splenectomy on the host's complex immune response, especially against normal and tumour allografts.