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Immunological responses of mice to threefold infection with infective Toxocara canis were studied up to 42 days. Mice of the experimental group were infected orally with 1000 infective eggs on days 0, 12, and 20 of the experiment (a total of 3000 eggs/mouse). The proliferative activity of spleen lymphocytes, production of specific antibodies in the serum, leukocyte counts, and T cells subpopulations in the blood and spleens were examined. The spleen T cells were significantly inhibited to 21 day post infection (dpi) while B cells were stimulated. An increased level of specific antibodies persisted almost the whole experiment. Leukocytosis with a dominant lymphocytosis was evident. In the peripheral blood the number of both CD8+ and CD4+ cells was significantly increased. Contradictory, a significant increase of the spleen CD8+ cells with a significant decrease of CD4+ cells was observed. In conclusion, the multiple high dose infection resulted in variable changes in the immune effector mechanisms. Some components were stimulated while others were inhibited which may suggest that immunosuppression is not the only major outcome of larval toxocarosis.