FIG 4.

Dutch but not Tanzanian volunteers show increased P. falciparum-specific in vitro IFN-γ production after CHMI. PBMCs collected pre- and post-CHMI from Dutch (D; circles; n = 9; post = 35 days after CHMI) and Tanzanian (T; squares; n = 21; post = 28 days after CHMI) volunteers were stimulated with PfRBC for 24 h. (A) After stimulation, cells were stained for surface expression of CD3, CD4, γδTCR, CD8, and CD56 to gate lymphocyte subsets. NKT and γδT were gated as a combined population. (B) Intracellular IFN-γ is shown for total lymphocytes after 24 h of uRBC or PfRBC stimulation. Graphs show the proportions of cells with P. falciparum-specific IFN-γ production, comparing Dutch and Tanzanian volunteers pre-CHMI (C) and post-CHMI (D), and comparing pre- and post-CHMI responses within each cohort for CD4⁺ T cells (E), CD8⁺ T cells (F), CD56dim NK cells (G), CD56bright NK cells (H), and NKT-γδT cells (I). For each volunteer, all time points were measured in a single experiment. Data are shown as whisker plots with boxes indicating the median with IQR and whiskers the minimum/maximum values (C and D) or individual data points with lines connecting the two time points for each volunteer (E to I). All responses were corrected for the background by subtracting responses to uRBC. Responses pre-CHMI and post-CHMI were compared using a Wilcoxon matched-pairs signed-rank test.