Eosinophilia and acquisition of resistance to Nematospiroides dubius in mice sensitized with adult worms.

BALB/c mice develop resistance to challenge with N. dubius third stage infective larvae (L3) 2-3 weeks after the administration of N. dubius worms. In contrast, CBA/H mice fail to develop resistance. Experiments were performed to test the hypothesis that the reason for the different behaviour of these mice was a difference in their eosinophil response. BALB/c mice and BALB/c leads to (BALB/c x CBA/H)F1 bone marrow chimaeras but not CBA/H mice or CBA/H leads to (BALB/c x CBA/H)F1 chimaeras mounted strong eosinophilia after N. dubius sensitization and the eosinophil response was associated with resistance to L3 infection in these mice. Induction of a mild eosinophilia in CBA/H mice by non-parasite antigen keyhole limpet haemocyanin (KLH) in complete Freund's adjuvant (CFA) following cyclophosphamide (CY) treatment was associated with the acquisition of a degree of resistance to L3 infection. In BALB/c mice, increase in eosinophilia induced by CY and KLH-CFA was not associated with a further reduction in worm numbers. These experiments support the hypothesis that eosinophilia is an important component of host protective immunity in vivo, and suggest a new basis for the heterogeneity of the outcome of some parasite infestations.