IgE-B cell-generating factor from lymph node cells of rats infected with Nippostrongylus brasiliensis. I. Source of IgE-B cell-generating factor

Culture supernatants of mesenteric lymph node cells obtained from Nippostrongylus brasiliensis (Nb)-infected rats have the ability to increase the proportion of IgE-bearing cells in normal bone marrow cell cultures. In order to determine the cell source of the active substance, mesenteric lymph node cells and thoracic duct cells from Nb-infected rats were fractionated by various methods, and culture supernatants of each fraction were examined for the ability to generate IgE-bearing cells in normal bone marrow cell cultures. It was found that culture supernatants of the B cell-enriched fraction were substantially more active than those of the unfractionated cells of T cell-enriched fraction. Residual activity in the culture supernatant of the T cell-enriched fraction was eliminated by prior removal of contaminating immunoglobulin (Ig)-bearing cells in the fraction. The mesenteric lymph node cells depleted of IgE-bearing cells by rosette technique failed to produce IgE-B cell-generating factor. The results indicated that a major source of the soluble factor is IgE-bearing B cells. This conclusion was supported by the fact that treatment of mesenteric lymph node cells with antibodies specific for IgE accelerated the formation of IgE-B cell-generating factor in culture fluids. Formation of IgE-B cell-generating factor by the mesenteric lymph node cells was reduced by pretreatment of the cells with pactamycin but not with mitomycin C, indicating that DNA synthesis is not required for the formation of the factor. The appearance of IgE-B cell-generating activity in the culture fluids of mesenteric lymph node cell cultures was inhibited in the presence of dibutyryl cyclic AMP or aminophylline but not by cyclic GMP.