In vivo suppression of delayed hypersensitivity by thiabendazole and diethylcarbamazine.

Several anthelminthic agents, such as niridazole and metronidazole, have been demonstrated to have striking effects on the immune system, apparently independent of their antiparasitic activities. In the present study, we have examined the effect of thiabendazole and diethylcarbamazine on two parameters of delayed hypersensitivity, lung granuloma formation around Schistosoma mansoni eggs and delayed footpad edema in response to schistosome egg antigens. Both drugs caused significant reduction of lung granuloma size in unsensitized animals when given as daily doses for 8 days. Thiabendazole was the more potent suppressant, affecting granuloma size in unsensitized animals when given as single dose and in sensitized animals using a multiple dose regimen. Diethylcarbamazine was without effect on granuloma size in sensitized animals, but inhibited delayed footpad swelling when given daily for 6 days. Neither drug affected granulomas induced by non-antigenic plastic beads. These data support the hypothesis that some of the clinical activities of these drugs may be mediated by interference with host response to antigenic stimuli.