Immunity to Trichinella spiralis VI. The specificity of the immune response stimulated by the intestinal stage.

Mice were immunized to the intestinal stage of T. spiralis by using infections terminated with methyridine before production of newborn larvae had commenced. The muscle larvae which encysted following a normal complete challenge infection were reduced by 87 and 95% in immunized mice. No statistically significant reduction in a challenge infection of intravenously injected parenteral larvae was produced (8% and 15% actual reduction). Previous work has shown that adult worms in a challenge infection are stunted and expelled earlier as well as having a reduced fecundity; it is concluded that the immunity generated by the intestinal stage is largely specific in its action to that phase in a challenge infection.