Therefore we further tested the hypothesis that cumulative malaria exposure is associated with skewing of monocytes towards an M2 regulatory phenotype by stimulating PBMCs of Malian children (aged 4–6 years; n = 9) and adults (n = 9), as well as U.S. adults (n = 9) with Pf-iRBCs for 18 hours and quantifying intracellular arginase 1 in monocytes by flow cytometry. This evidence concerns the gene ARG1 and malaria.