Flow cytometric evaluation of TRBC1 expression in tissue specimens and body fluids is a novel and specific method for assessment of T-cell clonality and diagnosis of T-cell neoplasms.

BACKGROUND: Flow cytometric detection of T-cell clonality is challenging. The current available methodology for T-cell receptor (TCR) Vbeta repertoire evaluation is a complex assay and has limited sensitivity especially for detecting low levels of disease. Therefore, there is an unmet need for a reliable, simple, and rapid assay to identify T-cell clonality. The rearrangement of the TCRB gene involves the random and mutually exclusive expression of one of two constant beta chain genes (TRBC1 and TRBC2), analogous to the kappa and lambda gene utilization by B cells. METHODS: Here, we used a single TRBC1 antibody, in conjunction with other T-cell associated markers, to detect T-cell clonality in tissue biopsies and body fluids. A total of 143 tissue/body fluid specimens from 46 patients with a definitive diagnosis of a T-cell neoplasm and 97 patients with no T-cell malignancy were analyzed with a cocktail of monoclonal antibodies including CD2/CD3/CD4/CD5/CD7/CD8/CD45/TCRgammadelta/TRBC1. RESULTS: We examined TRBC1 expression on neoplastic T-cell populations identified based on their immunophenotypic aberrancies, and monotypic TRBC1 expression was identified in all 46 known T-cell lymphoma cases. We applied a similar gating strategy to the 97 cases without T-cell neoplasms, and arbitrarily dissected T-cell populations into immunophenotypically distinct subsets; in this group, we found that all cases revealed an expected polytypic TRBC1 expression in all subsets. CONCLUSIONS: Single TRBC1 antibody detection of T-cell clonality by flow cytometry is a simple, rapid, and robust assay that could be routinely utilized in flow cytometric laboratories.