Potentiation of IgE response in vitro by T cells from rats infected with Nippostrongylus brasiliensis

The effect of T cells from rats infected with Nippostrongylus brasiliensis (Nb) on the IgE response was studied by using an in vitro system. Mesenteric lymph node cells from DNP-OA (dinitrophenyl derivatives of ovalbumin)-primed rats were cultured with DNP-OA or DNP-HSA in the presence of T or B cells from Nb-infected rats. It was found that T cells from the infected rat, but not normal T cells, selectively enhanced the IgE-forming cell response of DNP-OA primed cells to homologous antigen without affecting the IgG-forming cell response. The enhancement of the IgE response requires carrier primed T cells; T cells from Nb-infected animals failed to enhance the Ig-forming cell response of DNP-OA primed cells to DNP-HSA. Culture supernatants of T cells from Nb-infected rats selectively enhanced the IgE response of DNP-OA primed cells to homologous antigen without affecting IgG response. The IgE-potentiating factor present in the unstimulated cultures is different from T cell-replacing factor(s), which was obtained by stimulation of antigen-primed T cells with antigen. When T cells from Nb-infected rats were incubated with Nb antigen, culture supernatant of the cells enhanced both IgE and IgG responses of DNP-OA primed cells to DNP-OA or DNP-HSA. It was also found that the molecular size of IgE-potentiating factor was significantly smaller than T cell-replacing factor. The results suggested that an optimal IgE response may require two subsets of T cells; one is carrier-specific T cells, which are common for all isotypes, and another subset is cells forming IgE-potentiating factor.