Arrested rearrangement of TCR V[beta] genes in thymocytes from children with x-linked severe combined immunodeficiency disease

Human X-linked severe combined immunodeficiency disease (SCID) is an immunodeficiency disorder in which T cell development is arrested in the thymic cortex. B lymphocytes in children with X-linked SCID seem to differentiate normally. X-linked SCID is associated with a mutation in the gene that encodes the IL-2R [gamma]-chain. Because TCR-[beta] gene recombination is a pivotal initial event in T lymphocyte onteogeny within the thymus, the authors hypothesized that a failure to express normal IL-2R[gamma] could lead to impaired TCR-[beta] gene recombination in early thymic development. PCR was used to determine the status of TCR-[beta] gene-segment rearrangements in thymic DNA that had been obtained from children with X-linked SCID. The initial step in TCR-[beta] gene rearrangement, that of D[beta] to J[beta] recombination, was readily detected in all thymus samples from children with X-linked SCID; in contrast, V[beta] to DJ[beta] gene rearrangements were undetectable in the same samples. Both D[beta] to J[beta] and V[beta] to DJ[beta] TCR genes were rearranged in the thymic tissues obtained from immunologically normal children. The authors conclude that TCR[beta]-chain gene rearrangement is arrested in children with X-linked SCID. The results suggest a causative relationship between the failure of TCR [beta]-chain gene arrangements to proceed beyond DJ[beta] rearrangements and the production of a nonfunctional IL-2R [gamma]-chain. 45 refs., 3 figs.