Mechanisms of eosinophilia in Toxocara canis infected mice: in vitro production of interleukin 5 by lung cells of both normal and congenitally athymic nude mice.

Mechanisms of eosinophilia were compared between in vitro bone marrow cell cultures of congenitally athymic (nu/nu) mice and their heterozygous littermates (nu/+). Cultures of 5 x 10(4) bone marrow cells using interleukin 3 (IL-3), IL-5 and granulocyte-macrophage colony-stimulating factor showed that nu/nu and nu/+ mice mimicked each other in eosinophil production both before and after infection with Toxocara canis. Eosinophil differentiating activity (EDA) was detected in media conditioned by spleen cells and lungs of T. canis infected nu/+ mice, although nu/nu mice showed EDA only in lung-conditioned medium. EDA, detected both in infected nu/nu and nu/+ mice, was inhibited by an anti-IL-5 monoclonal antibody. These results indicate that IL-5 may be produced by lung cells of both nu/nu and nu/+ mice as well as by spleen cells of nu/+ mice infected with T. canis, which is the reason why nu/nu mice infected with T. canis exhibit blood eosinophilia.