Regulatory T cells decrease over time in individuals with high but not low malaria incidence.

<p>T_reg frequencies of CD4+ T cells (FoxP3+CD25+CD127^dim) were measured at 16, 24 and 36 months of age (PROMOTE- SP arm). <b>(A)</b> Children were divided into tertiles based on incidence of malaria between 16 and 36 months; lowest tertile median incidence 4.0 episodes ppy (IQR 3.0–5.5); intermediate tertile median incidence 8.2 episodes ppy (IQR 7.3–9.2); highest tertile median incidence 13.7 episodes ppy (IQR 10.3–14.6). The median duration since last malaria infection in these three tertiles was 8.5, 20, and 100 days, respectively. Wilcoxon matched pairs signed rank test p values indicated. Between 16 and 36 months, T_reg frequencies declined in individuals in the highest but not lowest tertile of malaria incidence. <b>(B)</b> Changes in T_reg frequencies between 16, 24 and 36 months were compared between children in the lowest, intermediate, and highest tertiles of malaria exposure by generalized estimate equations, accounting for repeated measures, age, duration since last malaria episode and parasite status at time of sampling.