Some factors affecting the cytotoxic immune reaction of rat mast cells

EARLIER investigations have shown that incubation of isolated rat peritoneal mast cells with purified anti-rat IgG-globulin and fresh serum in vitro results in a cytotoxic immune reaction1. Data demonstrating that this process is inhibited by various agents, especially by alkyl phosphates and synthetic chymotrypsin substrates, indicate that the activation of a chymotrypsin-like esterase is of some importance for the reaction2. The enzyme, which is contained in the heat labile serum portion, shows many striking similarities to an enzyme of the complement complex (C′1-esterase), and was therefore thought to be identical with it3. Further experiments, however, revealed that neither a euglobulin preparation with high C′1-esterase activity nor purified human (C′1a-esterase, irrespective of whether or not antibody is also present, produces detectable morphological or pharmacological changes in isolated rat mast cells (ref. 3 and Lepow, I. H., personal communication). The question thus arose as to what extent the immunological behaviour of mast cells would be influenced by pre-treatment with various enzymes. The data presented here provide some insight into the problem.