RATS RESISTANT TO THE DEXTRAN ANAPHYLACTOID REACTION

Abstract

In one colony of Wistar albino rats 23% were resistant to dextran and to egg‐white, these animals (non‐reactors) failing to show an anaphylactoid reaction after the intraperitoneal or intravenous injection of either of the two substances. Non‐reactors were also found in a few other colonies of Wistar rats but not in colonies of other strains. Procedures which potentiated the anaphylactoid reaction in sensitive rats (reactors) did not alter the response of non‐reactors. Dextran failed to release histamine from the perfused hind‐quarters of non‐reactors although other chemical liberators of histamine were effective. Lack of anaphylactoid reaction was not due to a deficiency of skin histamine or 5‐hydroxytryptamine, and the blood sugar and serum protein levels of non‐reactors were also normal. Non‐reactors could be sensitized to antigens and their serum was antigenic to guinea‐pigs. It is suggested that non‐reactors lack a blood or tissue component with which dextran normally combines to produce an intermediate substance active in releasing amines. 1963 British Pharmacological Society