The numbers of blood CD4+, CD8+, and CD4- CD8- T cells bearing αβ T-cell receptor (TCR) or γδ TCR molecules in males with a single missense mutation (L→Q271) in the common gamma chain gene (γc) were investigated by flow cytometry. Virtually all XCIDL→Q271 blood T cells that were CD4+ or CD8+ displayed αβ TCR but no γδ TCR. In contrast, CD4- CD8- T cells from affected males usually displayed γδ TCR, but no αβ TCR. The γδ TCR specificities were also studied. Except for the oldest subject, there was a direct relationship between blood CD3+ T cells that displayed γδ TCR and Vγ9 and Vδ2a specificities. Relative frequencies of CD3+ blood T cells that were Vγ9+ or Vδ2a+ were inversely related to age. In the oldest patient, the only detected γδ TCR specificity was Vδ1. Thus, in contrast to mice with no γc, XCIDL→Q271 blood T cells that bear γδ TCR with Vγ9/Vδ2a specificities develop but then decline in late childhood and thereafter. TCR with the Vδ1 specificity then appear in older survivors with XCIDL→Q271.
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