IGE ANTIBODY-PRODUCTION IS ASSOCIATED WITH SUPPRESSED INTERFERON-GAMMA LEVELS IN MESENTERIC LYMPH-NODES OF RATS INFECTED WITH THE NEMATODE NIPPOSTRONGYLUS-BRASILIENSIS

IgE and IgG2a antibody production and interferon (IFN)-gamma secretion were studied in rats infected with the gut nematode Nippostrongylus b rasiliensis by in vitro cultivation of mononuclear cells obtained from spleen (SPL), mesenteric lymph nodes (MLN) and pulmonary hilar lymph nodes (PLN). The highest levels of IgE were detected in the culture su pernatants of MLN cells after infection: IgE levels were modest in PLN and negligible in SPL. In contrast, the highest levels of IgG2a were produced by PLN cells, followed by MLN and SPL cells. These results in dicate that the MLN is the most significant site for IgE production in nematode infection, while IgG2a production is more marked in PLN. In naive rats, the spontaneous secretion of IFN-gamma was highest in PLN cells, followed by MLN and SPL cells. After the infection, IFN-gamma l evels were significantly decreased in MLN and PLN. Suppression of IFN- gamma secretion was also observed in concanavalin A (Con A)-stimulated MLN and PLN cells from infected rats. In MLN, the ratio of CD4(+) to CD8(+) T cells was increased after the infection. Stimulation with an allergen-rich, excretory-secretory (ES) substance of the nematode enha nced ongoing IgE production, and suppressed IFN-gamma secretion by MLN and PLN cells. In contrast, an allergen-poor, adult worm extract pote ntiated IFN-gamma secretion. These results show that nematode-induced IgE antibody response is associated with the suppressed production and /or secretion of IFN-gamma, particularly in the MLN, and that some mol ecules in the ES substance may trigger these immune responses.