Eosinophilia, granuloma formation and migratory behaviour of larvae in the congenitally athymic mouse infected with Toxocara canis.

Peripheral blood eosinophilia, histology of skeletal muscle and brain, and larval recovery were compared between congenitally athymic nude mice (nu/nu) and thymus-bearing heterozygous littermates (nu/+) for 6 weeks following oral infection with Toxocara canis eggs. By comparing patterns of peripheral blood eosinophil levels in nu/+ and nu/nu, two types of eosinophilias, one T cell dependent and the other independent, were observed. Eosinophil infiltration and granuloma formation around larvae in the skeletal muscle were weaker in degree in nu/nu than nu/+. The total number of larvae in nu/+ decreased from 2 to 6 weeks after infection. This decrease was directly related to a decrease in larval number in skeletal muscle, not in brain or other tissues. In contrast, no significant decrease of the total number of larvae was observed in nu/nu. The results indicate that eosinophilia, granuloma formation and larval recovery are closely related to cell-mediated immune mechanisms in T. canis-infected mice.