Uninfected erythrocytes, but not platelets or granulocytes, inhibit IFN-γ responses to malaria antigens. IFN-γ (pg/mL) was assayed in supernatants of PBMCs cultured for 6 days with 5 × 105/mL iRBCs (A) or 5 μg/mL PPD (B) in the presence or absence of purified erythrocytes, purified granulocytes, or purified platelets (all at concentrations equivalent to 1:3 dilution of whole blood) alone or in combination. Responses to uRBCs and GM were below the LDD of the assay (not shown); the pattern of responses seen with PfSL was identical to that seen for iRBCs (data not shown). No IFN-γ or proliferation was detected in cultures of erythrocytes, granulocytes, or platelets alone (ie, without PBMCs) (not shown). Data from 6 donors are shown. The dotted line indicates the LLD for the IFN-γ ELISA (125 pg/mL).
