CD4 and schistosomiasis: Another study, using major histocompatibility complex (MHC) class II or I mutant mice to examine the role of CD4+ and CD8+ T cells in the pathology of schistosomiasis, found that schistosome-infected MHC I mutant mice developed normal granulomatous lesions, while in contrast, MHC II mutant mice failed to form egg granuloma (121).