TRBC1 (T-cell Receptor Beta Chain Constant Region 1) and TRBC2 (T-cell Receptor Beta Chain Constant Region 2) are two gene variants that encode the constant region of the T-cell receptor beta chain. The detection of these chains by flow cytometry (FC) enables the identification of T-cell clonality in mature T-cell neoplasms (MTCNs).

In this study, we present a 13-color/15-parameter flow cytometry panel designed for the diagnosis and monitoring of MTCNs.

29 bone marrow samples, 91 peripheral blood samples, 7 lymphonodes and 5 cerebrospinal fluids were evaluated with clinical suspicion of MTCNs. These samples were labeled with TCRGAMADELTAFITC/TRBC1PE/CD8ECD/CD3PC5.5/CD56PC7/TRBC2APC/CD7APC700/CD4PC750/CD5PB/CD45KO/CD57BV610/CD16BV660/CD2BV780. Samples were acquired on DxFlex and analyzed on Kaluza (both Beckman Coulter). TRBC1 and TRBC2 monoclonal antibodies are clone JOVI.1 and SAM.2 respectively (both Beckman Coulter).

68 samples showed monoclonal T lymphocytes for TRBC1, 63 samples monoclonal for TRBC2. Furthermore, one sample presented a population of anomalous T lymphocytes expressing TRBC1 and another anomalous population expressing TRBC2. Of the cases that showed clonality, 40 were classified as Sezary Syndrome, 1 Adult T-cell Leukemia/Lymphoma, 15 T-Large Granular Lymphocytic Leukemia, 39 Mature T lymphoid neoplasms and 37 with T-cell clone of uncertain significance.

Detection of T-cell clonality is not limited to molecular techniques and specialized research laboratories, which often require longer turnaround times. FC is now routinely used to detect the beta chain variants, TRBC1 and TRBC2, on T cells. The analysis of these chains is valuable not only for identifying clonality but also for evaluating and monitoring MTCNs. However, the expression of TRBC1 and TRBC2 can vary among individuals due to genetic factors, age, health status, and other clinical conditions. Additionally, immunotherapy treatments may alter expression profiles, complicating data interpretation and disease monitoring. Despite these challenges, TRBC1 and TRBC2 detection remains a practical and informative tool in the clinical assessment of T-cell disorders.

The use of 13-color/15-parameter flow cytometry enhances sensitivity and specificity but demands extensive expertise in T-cell analysis. Success relies on advanced technology, quality antibodies, standardized protocols, and careful data interpretation. Our study demonstrates that TRBC1 and TRBC2 detection by flow cytometry is a valuable tool for assessing T-cell diversity and clonality, aiding in the diagnosis and monitoring of mature T-cell neoplasms.