FIG 5.

P. falciparum-specific in vitro IFN-γ production by innate lymphocytes from Tanzanian volunteers is dependent on baseline serological status. PBMCs collected from Tanzanian volunteers who either had a positive P. falciparum (Sero+; n = 12; black squares) or negative P. falciparum (Sero−; n = 9; white squares) serology prior to challenge (baseline) were stimulated with PfRBC for 24 h and stained for intracellular IFN-γ. Panels show IFN-γ production by lymphocyte subsets: (A) CD4⁺ T cells; (B) CD8⁺ T cells; (C) NKT-γδT cells; (D) CD56dim; (E) CD56bright NK cells. Data are shown as median ± IQR of responses corrected for the background by subtracting responses to uRBC. Differences in responses between the seropositive and seronegative groups were analyzed by a Mann-Whitney U test. P. falciparum-specific IFN-γ responses of pre-CHMI PBMCs from malaria-naive Dutch volunteers (D; n = 9; gray circles), who had negative P. falciparum serology, are shown as a comparator.