Further understanding of the mechanisms by which Notch receptors regulate the differentiation of IFNγ-secreting Th1 cells as well as the ligands involved in this process should contribute to the development of new vaccines and immunotherapeutic targets towards Leishmania pathology, as well as in other infections requiring protective IFNγ-secreting CD4+ Th1 immune response. The gene discussed is CD4; the disease is infection.