The Mechanism of Action of Heterologous Antilymphocytic Serum: The Biological Activity of Rabbit Macrophage‐cytophilic Antilymphocytic Antibody in Mice

Abstract

Summary. The existence and predonifnantly 7S nature of nmcrophage-t y tophi lie antiiwHly in r.ihbit anti-monsc lyinphocytt; st'rum has hcon tonfirnicd. Al>S()rption of rabl>il anti-iiiousc lymphocyte serum with liotnologous cflls reduced the titre of cytophilic activity deteniiined hy both direct and indirect methods, while most of the cytotoxic and agyhitinating activity was retained. Thi.s suKK"St'' the antibodies responsihlo for cytophilia exist as a separate claH.-i in rabl)it nnH-rnniise lymphocyte serum. Cvtophilif antibody also proinoteil the iittachincnt of thymus cells to Bidb/c matrophages both in vitro and in vivo, thi? attiulimcnt in the latter instance occurring only when the tliyinot-ytes were prc-iiuubatrd willi low antibody concentrations. Absorption nf rabbit anti-moiise lymphocyte sfruiii with rabbit tflts also rediic-ed ibJ ability in increase the localisation in the liver of injecti'd thynuicytes. while eluates of cytophilic antibody could promote significant uptake of these c-ells by the liver wheu incubated with them in vitro.The results generally confirm the opsonizing properties of rabbit anti-mouse lympliotyte .serum nnd indicate that rabbit cytophilic antibody is biolDgicMlly iiclivp ill mice.INTRODUCTION.