Although first identified as cells that limit autoimmune pro-inflammatory responses [14], nTreg (defined by expression of CD4, the transcription factor Foxp3 and high levels of CD25) have since been shown to regulate the immune response in a number infections including Leishmania spp infections, Mycobacterium tuberculosis and helminth infections [15]–[18], mediating their effects either via direct cell contact or by release of cytokines. This evidence concerns the gene CD4 and infection.