Action of diethylcarbamazine citrate on protective immunity in rats infected with Nippostrongylus brasiliensis

The effect of histamine on the immune response of hamsters to infection with Ancylostoma ceylanicum

The role of histamine in modulating the immune response of hamsters infected with Ancylostoma ceylanicum (hookworm) was investigated. Histamine administration (20 mg base/hamster x 6 ip) made the immune hamsters susceptible to challenge infection, and on assay the humoral as well as the cell-mediated responses were found to be suppressed. An adverse effect of histamine was observed on lymphocytes but the macrophage function remained unaltered, since the latter lack histamine receptors. These findings provide definite evidence that histamine suppresses specific immune responses, and that contrary to earlier reports this neurotransmitter does not play a direct role in the 'self-cure' phenomenon.

Effect of histamine and its antagonists on the course of Nippostrongylus brasiliensis in rats

The involvement of histamine in the rejection of Nippostrongylus brasiliensis (nematode) from rats harbouring 18 to 20-day-old infections was investigated. Parenteral administration of histamine delayed worm rejection. A similar effect was observed with histamine depletor, compound 48/80, and the prostaglandin synthesis inhibitor indomethacin. Antihistaminics, mepyramine and pyribenzamine failed to alter the course of infection, and neither did the histamine synthesis inhibitor, semicarbazide. Pretreatment of rats with the H1 histamine receptor antagonist, mepyramine, effectively antagonized histamine-induced worm retention, whereas the H2 histamine receptor antagonist cimetidine had a negligible effect. The results suggest that histamine or histamine depletors do not have any apparent role in self-cure mechanism; rather they support parasitism.