Cytokine mRNA expression in lymphoid organs associated with the expressionof IgA response in the rat

The T-helper dependency of the IgA antibody response has been investigated in rats injected intravenously with Schistosoma mansoni eggs. This method, allowing the trapping of parasite eggs in the lung tissue, led to a strong anti-egg IgA antibody response in the bronchoalveolar lavage but not in the serum. To characterize the cytokine pattern associated with the IgA respon se, kinetic analysis of the cytokine mRNA expression in the lungs, periaort ic nodes (PN) and spleen was undertaken. Under such conditions, significant levels of mRNA encoding IL-5 and IL-10 were recorded in spleen during the early period following egg injection, as well as a more prolonged expressio n of TGF-beta and IL-6 mRNAs. However, neither IFN-gamma nor IL-4 mRNA coul d be detected in these samples. Finally, in lungs and in PN, RT-PCR analysi s revealed delayed production of cytokine mRNA. Taken together our data sug gest that the rat mucosal IgA antibody response is predominantly linked to a Th2 response.