The effect of 5-hydroxytryptophan (5-HTP), iproniazid and reserpine on humoral antibody production was studied in C57B1 and BALB/c mice and rabbits. It was shown that intraperitoneal administration of 100 mg/kg 5-HTP to rabbits from the day of immunization results in decrease of agglutinin titer after primary immunization, while half of the dose (50 mg/kg) administered 2 days before immunization not only decreased the intensity of the primary and secondary immune responses, but also prolonged the latent period of antibody formation and changed the pattern of the secondary response to some extent. 5-HTP injected to mice caused a significant change in the intensity as well as in the pattern of the secondary immune response. Reserpine (1-2 mg/kg orally) exerted the same influence on antibody production as 5-HTP, the effect being most pronounced on the secondary immune response in mice. 100 mg/kg iproniazid injected intraperitoneally to mice produced some stimulation of antibody production in the early period of the primary immune response. Changes in the pattern of the secondary immune response were obtained only in some experiments. They were shown by delayed development of the response. In rabbits iproniazid administration in the dose of 10 mg/kg stimulated antibody production; 50 mg/kg iproniazid decreased antibody titer after primary and secondary stimulations and prolonged the latent period of antibody production. It is considered that inhibition of the immune response by reserpine, iproniazid and 5-HTP is related to their effect on the level of free serotonin. © 1968.
