The present study also demonstrates a predominance of IL-9 production in hepatosplenic patients with advanced fibrosis in SEA-stimulated cultures, in addition to correlations between this response and the spleen size, portal vein diameter, and periportal thickening, thus suggesting a role of the Th9 response in the pathogenesis of the severe form of human schistosomiasis. The gene discussed is IL9; the disease is fibrosis.