IgE formation in the rat after infection with Nippostrongylus brasiliensis. II. Proliferation of IgE-bearing cells in neonatally thymectomized animals.

Sprague-Dawley rats were infected with the helminth, Nippostrongylus brasiliensis , and the presence of IgE-bearing cells in various lymphoid tissues was examined by indirect immunofluorescence. An increase in IgE-bearing cells was detected in all lymphoid tissues except the thymus. In order to examine the importance of T cells in the proliferation of IgE-bearing cells and in the enhancement of IgE synthesis, neonatally thymectomized rats, which were unable to produce antibodies against a hapten-protein conjugate, were infected with N. brasiliensis . After infection, IgE-bearing cells appeared in all lymphoid tissues including the bone marrow. The kinetics of IgE-bearing cells and IgE synthesis were comparable in both thymectomized and nonthymectomized controls, however, the proportion of IgE-bearing cells in the mesenteric lymph nodes and spleen of thymectomized animals was about twice as high as that of nonthymectomized rats. At 14 days after infection of thymectomized rats, about 17% of total nucleated cells in the mesenteric lymph nodes bore IgE on their surface. These results as well as the appearance of IgE-bearing cells in the bone marrow of thymectomized animals suggested that T cells were not required for the development of IgE-bearing cells. By contrast, the serum IgE concentration and the number of IgE-forming cells detected in the mesenteric lymph nodes of thymectomized rats were significantly lower than that of nonthymectomized rats, indicating that the enhancement of IgE synthesis after infection was impaired by the absence of T cells.