Engagement of ICAM-1 with its cellular ligand but not with PfEMP1 is required for NK cell IFN-γ production.

<p>(A) Diagram of an ICAM-1 molecule showing schematic binding sites for LFA-1, Mac-1, CD11c/CD18 and PfEMP1. The epitope map of the anti-ICAM-1 mAb 15.2, My13 and RR1/1 is indicated. (B) Human PBMC were cultured with uninfected RBC (RBC, black bars) or with RBC infected with the 3D7 <i>Pf</i> strain (3D7, grey bars) in presence or absence of antibodies directed against NKG2D (isotype control), ICAM-1 or CD18. Three different clones of anti-ICAM-1 were used: 15.2 blocks the interaction of ICAM-1 with LFA-1 and with PfEMP1, RR1/1 blocks only the interaction with LFA-1 and My13 blocks only the interaction with PfEMP1. After 24 h of co-culture, NK cell activation was analyzed by flow cytometry by gating on CD3⁻CD56⁺ NK cells. The CD69 MFI staining on NK cells (left panel), the percentage of CD25⁺ NK cells (middle panel) and the percentage of IFN-γ⁺ NK cells (right panel) were determined for 24 donors (None, NKG2D and 15.2), 13 donors (CD18), 9 donors (My13) or 5 donors (RR1/1). Means ± SEM are represented. Statistical analyses were performed using the Mann Whitney test.