Nippostrongylus brasiliensis infection in rats. Both antibodies and sensitised cells are necessary for the immunological control of developing larvae.

A larval N. brasiliensis infection is expelled before reaching maturity in rats given both antiserum and sensitised lymphocytes but developing larvae are not expelled from rats given antiserum or cells alone. The immunity of animals given both components is as strong as immunity in actively immunised rats. The effects of immunity do not become evident until the larvae have migrated to the intestine. Developing larvae are more susceptible to the combined action of cells and antiserum than adult worms.