A Study of the Relation of Antibiotics, Vitamins and Hormones to Immunity to Infection

Abstract

It has been demonstrated that certain antibiotics, vitamins, and mammalian and plant hormones, administered in the host diet in adequate concentrations, can markedly influence the innate immunity of a host to a parasite. Thus, in Aedes aegypti the antibiotics penicillin, chloromycetin, and tyrothricin, the vitamin ascorbic acid, the mammalian hormones insulin and thyroxin, and the plant hormones indole-3-acetic acid, and β-naphthaoxyacetic acid, all increase host susceptibility to infection with Plasmodium gallinaceum. On the other hand, terramycin, thiamin, niacin, calcium pantothenate, biotin, and ACTH, all increase host resistance to this parasite. It has been demonstrated that drug concentration is so critical a factor in determining the qualitative effect of a compound that in certain cases a compound producing an increase in host resistance at one particular drug level will, within the same host, qualitatively reverse its effect at another level and produce instead an increase in host susceptibility to the same parasite. Thus, pyridoxine hydrochloride increases the resistance of A. aegypti to infection with P. gallinaceum, when administered in comparatively low concentrations, but reverses its effect and increases host susceptibility when administered in high concentrations, while inositol increases host susceptibility in lower concentrations and then increases host resistance when administered in higher concentrations. Finally, these results suggest that the innate immunity of a host to a particular parasite is a result of a summation of the interrelations, or of the reciprocal activities, of more than one system rather than the resultant of a single effective factor.