Background: Diagnosis of T-cell lymphomas can be challenging, and detection of T-cell monoclonality can make an important contribution. Assessment of T-cell monoclonality by flow cytometry has largely depended on determination of T-cell receptor Vβ expression. However, the standard Vβ panel uses 24 antibodies that only cover about 65% of cases, and require 8 tubes. Recently, detection of TRBC1 by the monoclonal antibody JOVI-1 has emerged as a potentially effective method for assessing clonal T-cell populations by flow cytometry. This approach is used because in each T-cell, the T cell receptor β chain gene uses either the TRBC1 or the TRBC2 gene.
Methods: In a prospective study, 99 patient samples of peripheral blood, bone marrow and other tissues were assessed for possible monoclonal T cell populations by 8-colour flow cytometry. The performance of TRBC1 was compared with that of TCR Vβ.
Results: There were 56 cases where either or both methods detected a monoclonal T-cell population, and 43 cases where both methods did not detect monoclonal T-cells. There was a very good level of agreement between the two methods. Of the 99 samples, 51 were monoclonal by both methods, 43 were not monoclonal by both methods and 5 samples were inconsistent. 4 of the inconsistent samples were monoclonal by TCRB1 but oligoclonal by TCR Vβ, and in 1 sample monoclonality was not detected by TCRB1 but was detected by Vβ. Compared against Vβ, TCRB1 was 98% sensitive and 91% specific.
Conclusion: Determination of TRBC1 with the JOVI-1 antibody is a reliable and efficient method for assessing T-cell populations for monoclonality by flow cytometry.