NK Cell IFN-γ Response to iRBCs Correlates with Accessory Cell Activation

<p>NK cell IFN-γ responses in PBMCs from eight malaria-naïve donors were analysed after 24 h of co-culture with iRBCs. The concentration in tissue culture supernatants of IL-12p70 and IL-2 was determined in a bead-based cytokine assay, and that of bioactive TGF-β by ELISA. The fluorescence intensities of CD40 and HLA-DR surface staining on CD14⁺ monocytes and the percentage of IFN-γ⁺ CD56⁺ NK cells were determined by flow cytometric analysis. Shown are the percentages of IFN-γ⁺CD56^bright NK cells (black squares) and IFN-γ⁺ CD56^dim NK cells (grey triangles), along with the correlation of the percentage of IFN-γ⁺ CD56^bright NK cells (black line) with the concentration of IL-12p70 and IL-2 in culture supernatants (A and B), with the MFI of CD40 and HLA-DR on resting monocytes (C and D), and with the up-regulation of bioactive TGF-β in culture supernatants (E). The correlation of TGF-β in culture supernatants with IFN-γ⁺ CD56^dim NK cells is also shown (E, grey line). Correlation coefficients are indicated for CD56^bright (upper values) and CD56^dim (lower values). Correlations were calculated using a second-order polynomial fit algorithm. Black arrows indicate examples of donors where IFN-γ response is highly suppressed in the CD56^dim NK cells. Flow cytometric data are based on the collection of 100,000 total events.