RESUMO
Mutations in T-cell antigen receptor (TCR) subunit genes cause rare immunodeficiency diseases characterized by impaired expression of the TCR at the cell surface and selective T lymphopenia. Here, detailed analyses of spontaneously arising somatic mutations that recover CD247, and thus TCR expression, in a newly identified CD247-deficient patient are described. The recovery of CD247 expression in some patient T cells was associated with both reversion of the inactivating mutation and a variant with a compensating mutation that could reconstitute TCR expression, but not as efficiently as wild-type CD247. Multiple mutations were found in CD247 complementary DNAs (cDNAs) cloned from the patient as well as in cDNA and genomic DNA from other individuals, suggesting that genetic variation in this gene is frequent. Analyses of other genes mutated in primary immunodeficiency diseases (PIDs) where reversions have been described also revealed a higher rate of mutation than that observed for genes mutated in PIDs where revertants have not been identified or control genes. These data support the hypothesis that the occurrence of somatic mutations that may reconstitute genetic defects in PID is related to an increased propensity of those genes to mutate.