EVIDENCE THAT RADIO-SENSITIVE CELLS ARE CENTRAL TO SKIN-PHASE PROTECTIVE IMMUNITY IN CBA/CA MICE VACCINATED WITH RADIATION-ATTENUATED CERCARIAE OF SCHISTOSOMA-MANSONI AS WELL AS IN NAIVE MICE PROTECTED WITH VACCINE SERUM

Naive CBA/Ca mice and CBA/Ca mice vaccinated 4 weeks previously with radiation-attenuated cercariae of Schistosoma mansoni were subjected to 550 rad of whole body (gamma) irradiation and then challenged 3 days later with normal cercariae. The perfusion recovery data showed that this procedure reduced the primary worm burden in naive mice by 22 % and the challenge worm burden in vaccinated mice by 82 %. Irradiation also ablated the peripheral blood leucocytes of both mouse groups by 90–100% at the time of challenge. Histological data revealed that such treatment caused a dramatic change in number, size and leucocyte composition of cutaneous inflammatory skin reactions that characterize challenged vaccinated mice and are known to entrap invading larvae; cutaneous eosinophils were preferentially abolished by this treatment. Polyvaccine mouse serum that conferred protection passively upon naive recipient mice, failed to protect naive/irradiated mice when administered by the same protocol. Distraction of macrophages by treatment of mice with silica did not affect the establishment of a primary worm burden and reduced the protection exhibited by vaccinated mice by only 16%. These data indicate that radio-sensitive cells are important to both innate and specific acquired resistance in this mouse model and that macrophages contribute only marginally to the expression of vaccine immunity. © 1990, Cambridge University Press. All rights reserved.