SLAM family receptor expression on XLP or healthy donor CD8⁺PBMC or T-cell clones. Flow cytometry was used to measure surface level expression of SLAM family receptors on CD8⁺ PBMCs (A) or T-cell clones (B) from 2 healthy donors or XLP1 and XLP8. Cells were stained with antibodies specific for CD8 and costained with either antibodies specific to the indicated SLAM receptors or isotype control antibodies. Histograms present the analysis gated on CD8⁺ positive cells, with the intensity of SLAM family receptor staining shown in black or isotype staining in gray.