Relative expression of mHAg-encoding genes in different human tissues. Real-time PCR was used to determine the relative expression levels of the P2RX7, DPH1, and DDX3Y genes in different human tissues. Expression of the hematopoietic-specific CD45 gene was also determined to permit estimation of the extent to which each of the tissues examined was contaminated by cells of hematopoietic origin. For each gene, the relative expression level was defined as the expression level of that gene in a specific tissue compared with its expression level in male EBV-LCL. ▩ indicates expression level of each gene in the spleen and PBMCs to facilitate their comparison with the expression levels in nonhematopoietic tissues.