Cellular and humoral immune response in mice with a long-term Toxocara canis reinfection

The proliferative response of splenic T and B cells to nonspecific polyclon al activators (concanavalin A, lipopolysaccharide and pokeweed mitogen), sp ecific circulating antibody level and macrophage metabolic activity were st udied in mice reinfected every seven days of the experiment (140 days) with a dose of 50 Toxocara canis eggs per mouse. Significant differences have b een found in the proliferative activity of T and B cells, depending on the source of serum used in the culture medium. In vitro incubation of infected mouse lymphocytes in foetal calves serum significantly increased the proli ferative activity of both the cell populations to all mitogens on day 14 of experiment. On the contrary, lymphocytes incubated in autologous serum fro m infected mice showed their proliferative activity suppressed to all mitog ens as early as on day 14 of experiment, with inhibition of B cell prolifer ation persisting throughout the experiment. With incubation of infected mou se lymphocytes in serum from healthy mice, only T cells showed an inhibited response to concanavalin A, persisting on day 28 for the duration of the e xperiment, while the B cell response to lipopolysaccharide was markedly sti mulated on day 42 of experiment. Specific anti-toxocara circulating antibod y level was increasing conspicuously from the beginning of the experiment, with the maximum reached on day 56. In the same period, also peritoneal mac rophage metabolic activity increased significantly. The results suggest a p artial suppression of nonspecific polyclonal activation of T and B cells an d the stimulation of macrophage metabolic activity and antibody response of mice after their long-term reinfection.