Bronte Jeffrey¹, Marisa Alves¹, Steven Le¹, Elizabeth Foley¹, Samuel Breit^1,2,3 ,William Sewell^{1, 2,4}

¹Department of Immunopathology, Sydpath, St Vincent’s Hospital, Sydney, Australia

²School of Medicine, University of New South Wales, Sydney, Australia

³St Vincent’s Centre for Applied Medical Research (AMR), St Vincent's Hospital. Sydney

⁴The Garvan Institute of Medical Research, Sydney, Australia

Background: Diagnosis of mature T cell neoplasms by flow cytometry is challenging. Historically, Vbeta antibodies have been used to assess T cell clonality. This approach,  however,  has lacked sensitivity, is costly and time consuming. More recently, TRBC1 and TRBC2 antibodies which target mutually exclusive isoforms of the constant beta chain of the T cell receptor have been introduced as an alternative means of clonality assessment. These antibodies have the potential to simplify T cell analysis.

Methods: Specimens referred for flow cytometry were simultaneously analysed with TRBC1 alone and combination TRBC1/TRBC2. 

Results: 139 specimens were analysed for clonal T cell populations. This included 106 control specimens, 16 samples in which a T cell population of uncertain significance (T-CUS) was reported and 17 samples with confirmed T cell neoplasm.  All 17 specimens with confirmed T cell neoplasm were clonal using TRBC1 alone and combination TRBC1/TRBC2 analysis. Overall, prevalence of T-CUS was high with clones identified in 33 (32%) of control specimens.  Furthermore, use of the TRBC1/TRBC2 combination clarified analysis and 11 T-CUS specimens had different clonality using the combination compared to TRBC1 alone.

Conclusion: Combination  TRBC1/TRBC2 antibody in T cell analysis increases certainty in reporting clonal populations compared to TRBC1 alone.