Recombination pattern of the TCR gamma locus in human peripheral T-cell lymphomas.

The recombination events of the gamma and beta T-cell receptor (TCR) loci were analysed in a series of 39 peripheral T-cell lymphomas (PTCLs) in association with the expression of TCR chains. In TCR alpha beta PTCLs, 22/23 cases showed a gamma-gene rearrangement while only 18/23 showed a concomitant beta-gene rearrangement. The germline configuration of the beta locus was found in angiommunoblastic lymphadenopathy and lymphoepithelioid lymphomas. Three gamma delta PTCLs rearranged both gamma and beta genes. TCR silent PTCLs showed three different patterns of gamma- and beta-gene rearrangements. Three cases were in germline configuration for both loci; five cases had a rearranged gamma and a germline beta locus; and five cases had the two loci rearranged. Regarding the variable genes in the gamma-rearranged alleles, members of the V gamma I subgroup were the most frequently presented (39/50), followed by V gamma II, V gamma III, and V gamma IV (9/50, 1/50, and 1/50, respectively). Joining segment usage was as follows: J1 or J2 (32/50), JP1 or JP2 (17/50), and JP (1/50). Taken together, these data demonstrate that the gamma locus is more frequently rearranged whatever the TCR expression. The gamma-locus analysis provides a better diagnostic yield than the beta locus in the study of PTCL clonality.