Tadaki DK, Craighead N, Saini A, Celniker A, Burkly LC, Lee KP, Chute JP, Harlan DM, Kirk AD. Costimulatory molecules are active in the human xenoreactive T-cell response but not in natural killer-mediated cytotoxicity. Transplantation. 2000 Jul 15; 70(1):162-7.