Because SAP/SH2D1A deficiency was identified as the cause of aberrant T-cell control of EBV in XLP-1 and EBV-specific T-cell activity was known to be reduced in patients with RA, we quantified the level of SAP/SH2D1A mRNA in the peripheral blood T cells of patients with RA. This evidence concerns the gene SH2D1A and rheumatoid arthritis.