To investigate whether the propensity of CD4 T cells to differentiate into Tregs in response to parasite antigen is influenced by age and/or prior malaria exposure, we measured induction of Tregs following in vitro stimulation with P. falciparum schizont extracts (PfSE) in malaria-naïve adults, malaria-exposed children (28 months of age), and malaria-exposed adults from the high incidence district of Tororo (gating strategy and ex vivo Treg frequencies shown in S4 Fig). This evidence concerns the gene CD4 and malaria.