A PCR assay for detecting clonal rearrangement of the TCR-gamma gene

The T-cell receptor gamma chain (TCR-gamma) gene has 11 functional variable (V) exons that can be organized into four subfamilies and four functional joining (J) exons that can be divided into two subfamilies.

Three multiplex PCR reactions amplifying the TCR-gamma gene were developed. Primer combinations for multiplex PCR were chosen so that the V-region subfamily and J-region subfamily involved in a clonal band could be identified. Control primers from the protease inhibitor (PI) gene were also included in each reaction to verify the presence of amplifiable DNA. Fifty-six archived samples that had been tested by Southern blot for clonal rearrangement of the TCR-beta gene were analyzed with the TCR-gamma PCR protocol. Twenty-one of 56 samples were TCR-beta positive by Southern blot and thus expected to be positive with TCR-gamma PCR. Thirty-five of 56 samples were TCR-beta negative by Southern blot. Of these, 14 samples showed clonal rearrangement of the immunoglobulin heavy chain gene. The TCR-gamma PCR protocol showed a diagnostic sensitivity for detecting T-lineage clonality of 90%, with a diagnostic specificity for detecting T-cell lineage of only 74%.

The PCR protocol described here performed well in comparison with a TCR-beta Southern protocol.