Intratracheal instillation of cytoplasmic granules from phleum pratense pollen induces IgE and cell-mediated responses in the brown Norway rat

Abstract : Release of cytoplasmic granules from grass pollen upon contact with water is thought to be an important source of airborne allergens. To investigate the humoral and cellular responses to intratracheal instillation of Phleum pratense (timothy grass) pollen cytoplasmic granules (PCG) in the Brown Norway rat. PCG were purified from timothy grass pollen by filtration through 5-mum-mesh filters. Rats were sensitized (day 0) and challenged (day 21) intratracheally with purified PCG suspended in saline (6 x 10(6) PCG/rat). Rats were then challenged 4 weeks later (1.5 x 10(6) PCG/rat). Blood samples, bronchial lymph nodes and lungs were collected from the rats 4 days after the second challenge. PCG-specific IgE and IgG1 levels and specificity were determined by ELISA and Western blotting. Pollen, pollen extract and PCG-induced proliferation of lymph node cells were monitored by [H-3]-thymidine incorporation in a lymph node assay. Histopathological examination was carried out on the lungs. Specific IgE and IgG1 were present in the sera. Cultured lymph node cells proliferated in the presence of pollen, pollen extract and PCG. Western blots showed that all major pollen allergens are recognized by IgE and IgG1 from PCG-treated rats. Histopathological examination revealed features of a mild allergic reaction. In our rat model of allergy, purified timothy grass PCG instillation induced specific antibodies and lymph node cell responses, comparable to those obtained with intact pollen.