TAP2^−/− NK cells are unable to kill autologous PHA blasts.

(A) Polyclonal NK cell populations derived from E.M.O. or from E.F.A. and 2 clones from E.M.O. displaying the NCR^brightphenotype were assessed for cytolytic activity against E.M.O. PHA blasts either in the absence (white bars) or in the presence (black bars) of anti-HLA class I mAb. Controls were represented by 2 clones (CB1 and CB2) derived from a healthy donor that were analyzed against E.M.O. PHA blasts and against autologous PHA blasts (CB PHA blasts). The E:T ratio used in this representative experiment was 10:1. (B) HLA class I surface density on the indicated cell populations derived from E.M.O. and from a healthy control donor. The different cell types were stained with anti-HLA class I mAb (A6/136 IgM) and then were analyzed by cytofluorometry. HLA class I expression levels in cells derived from E.F.A. were comparable to those detected in E.M.O.