Spleen cell responses in experimental murine toxocariasis.

Splenic responses of CBA/J mice infected with 250 embryonated ova of the nematode, Toxocara canis were characterized during the first month post-inoculation (P.I.). By the 6th day of infection, spleen to body weight ratios were over 3.5 times greater in infected mice than uninfected controls. This ratio peaked at 5.0 on day 14 and declined slightly by day 36 P.I. Lymphocyte transformation studies were carried out using the T cell mitogens, Con A and PHA and the B mitogen, LPS. The responses of infected mice to all of the mitogens were greater than or equal to the responses of uninfected mice at all times studied. Unstimulated lymphocytes from infected mice spontaneously incorporated approximately 10-fold more 3H-TdR than did uninfected control mice during the first 2 weeks of infection. Antigen-specific lymphocyte transformation was also performed using a crude extract of homogenized embryonated ova (TEE) as the antigen. Positive responses were obtained at all times examined but were greatest during the first 2 weeks of infection. The T cell basis of this response was demonstrated by Anti-Thy 1.2 plus complement treatment prior to the initiation of the lymphocyte transformation assay. Collectively, these results suggest that in mice, T. canis elicits a striking splenomegaly as early as 1 week after oral inoculation. The lymphocyte transformation studies suggest that the splenomegaly may be due in large part to proliferation of the white pulp based on the amount of spontaneous labelling observed. Increased mitogenic responses indicate that T. canis does not elicit nonspecific immunosuppression and the positive response to the TEE antigen suggests that at least some of the lymphoproliferation is antigen specific.