In accordance with these findings, a study by Hisaeda and colleagues indicated that differential activation of natural regulatory T cells (nTreg) may account for the differing virulence of P. yoelii strains, since depletion of CD4+CD25hi T cells (with anti-CD25 antibody) prior to infection converted PyL from a rapidly lethal infection into a resolving infection but had no effect on the course of PyNL infection [13]. This evidence concerns the gene SFRP4 and infection.