IgE antibody responses in bronchoalveolar spaces of rats infected with Nippostrongylus brasiliensis

Abstract

IgE levels in the bronchoalveolar lavage fluids (BALF) of rats increased significantly following infection with Nippostrongylus brasiliensis. This increase corresponded with a concurrent increase in serum IgE levels. However, a comparison of IgE to albumin ratio in both BALF and serum suggested local accumulation and/or production of IgE in the bronchoalveolar spaces rather than leakage from serum. Subsequent analysis of BALF showed presence of heat-labile PCA activity with highest anti-worm titer (1:64) on Days 11-16 postinfection (pi). Secondary infection resulted in up to a fourfold increase in PCA activity compared to primary infection. Immunoblot analysis showed that these parasite-specific IgE antibodies in BALF recognized many proteins of adult worms ranging from 16-290 kDa. IgE antibodies in serum and BALF showed similarities in their reactivities toward adult worm antigens. However, the IgE antibody reactivities to different antigens varied significantly among different days pi. Depletion of IgG from BALF and serum resulted in more intense binding by IgE antibodies to antigens than when IgG was not depleted. Concurrent with the elevated levels of IgE antibodies, there was a significant increase in the levels of histamine in BALF, suggesting activation of mast cells. Thus, following N. brasiliensis infection there is an abundance of parasite-specific IgE antibodies in the lower respiratory tract and IgE-mediated pathways of inflammation appeared to be activated in the lungs.