Because Arg-1 and iNOS activities are regulated by the availability of L-arginine [17] and alternatively-activated macrophages play an important role in the pathogenesis of schistosomiasis [9],[10], we examined whether CAT2 deficiency was regulating the function of alternatively-(AA) or classically- (CL)-activated macrophages. The gene discussed is SLC7A2; the disease is schistosomiasis.