Cytokine mRNA expression in lymphoid organs associated with the expression of 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 response, kinetic analysis of the cytokine mRNA expression in the lungs, periaortic 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 expression of TGF-beta and IL-6 mRNAs. However, neither IFN-gamma nor IL-4 mRNA could be detected in these samples. Finally, in lungs and in PN, RT-PCR analysis revealed delayed production of cytokine mRNA. Taken together our data suggest that the rat mucosal IgA antibody response is predominantly linked to a Th2 response.

Molecular characterization of a partial sequence encoding a novel Schistosoma mansoni serine protease

A PCR strategy using degenerate oligonucleotide primers based upon consensus sequences of the active site of serine proteases yielded a 467 bp fragment from genomic DNA from Schistosoma mansoni cercariae. The sequence presented a continuous open reading frame and the deduced amino acid sequence (156 aa) presented homologies with various serine proteases, in particular the highest percentage identity was observed with a mammalian plasma kallikrein. The expression of this serine protease was studied first at the mRNA level and it was only detected by RT-PCR in cercariae and in adult worms. At the protein level we were able to detect it by Western blotting and by using antigen extracts from metabolically radio-isotope labelled worms. The absence of any positive signal in Northern blot and the detection of the protein suggest that the mRNA has a very short half-life, however the protein may be accumulated in the parasite. The significance of identity with mammalian kallikrein was confirmed by cross-immunoreactivity with a native porcine pancreatic kallikrein. However, no cross-reactivity was observed with S. mansoni elastase, another serine protease. Thus, we suggest that the serine protease described in this paper is a kallikrein-like protease.