Recognition of LCL targets in the presence of SLAM receptor blocking antibodies by CD8⁺T-cell clones derived from healthy donors or XLP patients. (A) CD8⁺ T cells specific for the KRP-epitope derived from a healthy donor (left panel) or XLP1 (right panel) and HLA-B*2705 matched or mismatched LCLs or (B) CD8⁺ T cells specific for the YVL-epitope derived from a healthy donor (left panel) or XLP8 (right panel) and BZ⁺ HLA-A*0201 matched or ΔBZ LCLs were incubated with the indicated antibodies at a concentration of 10 μg/mL for 30 minutes. The CD8⁺ T cells and targets were then mixed in the presence of the antibody and T-cell recognition assessed by measuring IFN-γ secretion after overnight incubation. LCLs sensitized with the cognate peptide served as positive controls. (C) CD8⁺ T cells specific for the YVL-epitope derived from a healthy donor (left panel) or XLP8 (right panel) were incubated with target LCLs sensitized with either a high concentration of peptide (0.5μM) or a suboptimal concentration of peptide (0.05μM) or DMSO as a control. LCLs sensitized with the suboptimal concentration of peptide or DMSO and the T cells were incubated with the indicated antibodies as above and these used in 5-hour chromium 51 release cytotoxicity assays. Asterisks indicate results which are significantly different from the no antibody treatment control using the Mann-Whitney U test (P < .05).