Immunity to Brugia pahangi in athymic nude and normal mice: eosinophilia, antibody and hypersensitivity responses.

Congenitally athymic nude (nu/nu) mice, immunologically reconstituted by thymus grafting before inoculation with infective larvae, and mice heterozygous for the nu gene (nu/+), mounted potent protective humoral and cellular immune responses to Brugia pahangi. Although responses were not identical, both groups of mice produced IgM, IgG and IgE antibodies specific for adult worm antigen (S-Ag) present in a crude aqueous extract, made immediate and delayed hypersensitivity footpad swelling responses when challenged with S-Ag and eliminated their infection in the early larval stages. Heterozygotes also exhibited a marked eosinophilia which peaked coincident with larval killing. In contrast, thymus grafting of patent nudes had no effect upon microfilaraemias or adult worm burdens and did not completely protect against a challenge larval inoculum although antibodies specific for S-Ag were produced. With the occasional exceptions of moderate immediate footpad swelling and very low titres of IgM specific for S-Ag, no specific immune responses to B. pahangi were found in ungrafted nude mice which allowed full development of adult worms and supported patent infections.