Although IL-4 is classically associated with CD4+ TH2 differentiation and associated immune responses, it is also important in regulating CD8+ T cell responses during bacterial and parasitic infections [8], [9] and more recently has been demonstrated to be required for the development of a population of CD8+ innate-like lymphocytes (ILLs) [10]–[15]. This evidence concerns the gene CD8A and parasitic infectious disease.