Phenotypes of Heligmosomoides polygyrus selected to survive protective immunity in quackenbush mice

The survival of Heligmosomoides polygyrus phenotypes passaged selectively through naive (Hpn) and immune (Hpa) outbred Quackenbush (Q) mice was compared in Q mice immunized passively with normal (NMS) and immune mouse serum (IMS). IMS raised against Hpn(Q) worms (IMS-N) was 93% and 92% protective against Hpn(Q) and Hpa(Q) phenotypes, respectively; IMS against Hpa(Q) (IMS-A) conferred 93% protection against the Hpn(Q) phenotype but gave only 45% protection against the adapted Hpa(Q) parasites (P < 0.01). IMS-A had less anti-parasite IgG reactivity than did IMS-N (P < 0.05). A 34-kDa antigen from male Hpn(Q), but not Hpa(Q) worms, and an antigen at 56 kDa in male Hpa(Q), but not Hpn(Q) parasites, reacted on immunoblots with both sets of IMS. Thus, it appeared that Hpa(Q) worms endured higher levels of protective immunity than did Hpn(Q) worms and that Hpa(Q) and Hpn(Q) phenotypes had different antigens, which, however, did not lead to phenotype-specific immunity. This reflects the complexity of host-parasite interactions.