The expansion of Treg cell population during the early CD4+ T cell response to infection may be essential for the development of a cohort of Treg cells shaped to modulate the pool of effector-memory and memory CD4+ T cells generated during the late phase of the response, by skewing their specificity repertoire towards the recognition of parasite-specific peptides and avoiding the expansion of self (cross) reactive clones. The gene discussed is CD4; the disease is infection.