Specificity and antibody blocking of CTL clone B-24. Direct cytotoxicity (A) and IFN-gamma ELISPOT (B) of B-24 CTL against various target cells. Blocking of cytotoxicity (C) and IFN-gamma ELISPOT (D) of B-24 CTL by various antibodies. The number of B-24 cells used in the IFN-gamma ELISPOT assays (B and D) was 5000. The number of target cells in A and B was 1x10⁴. pRL1a pulsed P1.HTR cells (1x10⁴) were used as targets in C and D. Effector to target cell ratio in C was 10. Antibody dilution in D was 1/100. Refer to the text for details.