A-159 Role of TCRB1 Antibody in the Evaluation Panel of T Lymphoproliferative Diseases

Abstract

Abstract Background The diagnosis of T lymphoproliferative diseases is usually a challenge due to the difficulty indifferentiating pathological T cells from reaction cells and also due to the limitation of clonalitytests currently available. TCRB1 is a monoclonal antibody specific for region 1 of the TCR T cellreceptor Beta chain constant, detecting clonal populations of TCRab positive T cells in caseswhere its expression is monotypic. Its application is similar to immunoglobulin light chainrestriction in the detection of B cell lymphoproliferations and in normal T CD3 + TCRab + cells, theexpression of this marker is polytypic. The objective of the present work is to report theexperience of including this antibody in the lymphoproliferative T panel in a private laboratoryin southern Brazil. Methods Samples received with indication of lymphoproliferative disease and lymphocytosis wereevaluated using the tube Lymphocyte Screnning Tube—LST (Euroflow) and were acquired usingFACS CANTO or FACS LYRIC cytometers. Analyzes were performed using Infinicyt software. After, all, samples that showed alteration in the CD4/CD8 ratio, or antigen alteration in the expressionof pan T markers were evaluated for the complete investigation panel according to Euroflowprotocol. This panel had the incorporation of the tube for the evaluation of clonality that hasthe TCRB1 antibody in the PE channel associated with the anchor markers CD45V500, CD3PerCpcy5, CD4V450 and CD8APCH7. The channels that were not used (FITC, APC, Pecy7) areused when necessary, to evaluate antigens that can help select the desired aberrant population,such as CD5, CD2, CD7 antibodies or to assess maturation, like CD45RA and CD27. Data werecollected from the beginning of the use of this antibody from February 2021 until the presentmoment. Results During this period, 2870 samples for immunophenotyping analysis were received, of which 17cases were T chronic lymphoproliferative diseases. Of the 17 cases found, 11 (65%) were caseswith the pathological population TCRab positive and the expression of TCRB1 could beevaluated. In these cases, the expression of the patologic cells was monotypic for the TCRB1antigen. The cases were: 4 large granular lymphocytic (LGL) leukemia, 4 Adult T-cellleukemia/lymphoma /Peripheral T-cell lymphoma, unspecified , 1 Sezary syndrome, 1 T-celllymphoblastic lymphoma in cortical/common thymocyte stage and 1 T-cell prolymphocyticleukemia (T-PLL). Recent studies have demonstrated the high specificity of this test for clonality, as long as it is associated with an expanded and standardized lymphoproliferative panel. Thepresent cases demonstrated good results for peripheral blood samples, bone marrow and lymphnode biopsy. Conclusion T-lymphoproliferative disorders remain a diagnostic challenge, due to the difficulty of a simpletest to assess clonality. The inclusion of the TCRB1 antibody in the lymphoproliferative panelincreased the specificity of the test for diagnosis, being a method of rapid execution and lowcost. Another advantage of using this marker is the possibility of evaluating small cell clonesthat may not be detected in molecular biology techniques due to the sensitivity of the test.