Regulation of macrophage phagocytosis of syngeneic erythrocytes by T-cell subsets from NZB mice: differential effects of T cells from young and old mice.

The regulation of syngeneic erythrophagocytosis (EP) by macrophages (M phi) harvested from young and old NZB mice was examined by spectrophotometric assay and morphological observation. Peritoneal exudate M phi from young NZB mice weakly ingested syngeneic red blood cells (RBC). T cells derived from old NZB mice accelerated ingestion of RBC by young M phi. On the contrary, T cells from young NZB mice suppressed EP by young T cells appeared clearly when they were added to M phi derived from old mice, which ingested syngeneic RBC actively without help by old NZB T cells. Namely, such an active EP by old M phi was completely suppressed when they were incubated with young T cells. Simultaneous addition of both young and old T cells to either young or old NZB M phi with RBC suppressed the EP. Pretreatment of young T cells with anti-Lyt 1.2 antibody and complement (C) made the suppressive activity prominent, and preincubation with anti-Lyt 2.2 and C eliminated the suppressive activity, but gave rise to the enhancing activity. Young T-cell homogenates added to younger or old M phi together with RBC did not reveal suppressive activity for EP, and on the contrary facilitating activity appeared predominantly. Young and old T-cell homogenates added together to young M phi did not suppress EP. The largest of T-cell-factor accelerating EP was M phi, but not RBC. M phi with active EP belong to Ia-bearing subpopulations.