Schistosomiasis leads to significant morbidity and mortality, associated primarily with the production of eggs by schistosomes. Our previous studies, using a murine model of Schistosoma mansoni infection, demonstrated that schistosome development in the mammalian host require the presence of host CD4 T cells to complete their development normally. Our goal was to elucidate whether the activation of CD4 T cells to schistosome worm antigens is necessary for the development of schistosomes in early infection. CD4 T cell responses that occur earlier in schistosome infection are of considerable interest because of their potential ability to kill migrating schistosomula and mediate protection against infection. We therefore initiated studies to better characterize the early CD4 T cell responses to schistosome worm antigens in greater detail.