Experimental immune-mediated blepharoconjunctivitis in rats induced by immunization with ragweed pollen

Background: A study was performed to compare the effects of immunization with ragweed pollen (RW) in two different adjuvants on the characteristics of a previously described model of experimental immune-mediated blepharoconjunctivitis (EC) in rats. Methods: Lewis or Brown Norway (BN) rats were immunized with 100 mu g of RW in emulsion with aluminum hydroxide [Al(OH)(3)] or complete Freund's adjuvant (CFA). Three weeks later, the animals were challenged with eye drops containing RW in PBS. Twenty-four hours after topical challenge, eyes, blood, and lymph nodes were obtained for histology, measurement of antigen-specific antibodies, and proliferation or cytokine assays, respectively. In addition to active immunization, recipients of RW-primed lymph node cells were challenged and evaluated as above. Results: RW in both adjuvants induced infiltration with predominantly mononuclear cells in Lewis rats and eosinophils in BN rats. As well as active immunization, eosinophils were detected only in BN rats by adoptive transfer of cells. Lymphocyte proliferative responses to RW were high in immunized Lewis rats when CFA was used as an adjuvant. In contrast, proliferative responses in BN rats were higher when Al(OH)(3) was used, RW-specific IgE was detected only in BN rats. There were no significant differences in RW-specific IgG1/gCr2a ratio among the four groups. Lewis rats had higher level of RW-specific interferon-gamma in the culture supernatant. Conclusions: The characteristics of EC are different in Lewis and BN rats, dependent on the genetic background of the rat strains. The response to RW was similar to other previously used antigens, such as ovalbumin.