b'TRB Clonality AssayClinical InformationThe human T-cell receptor beta (TRB) gene locus onThese developmentally regulated, programmed gene chromosome 7 (7q34) includes 64-67 variable (V) generearrangements generate combinations that are unique segments (belonging to 30 subgroups), 2 diversity (D)for each cell. 1Since leukemias and lymphomas originate gene segments, and 13 joining (J) gene segments, spreadfrom the malignant transformation of individual lymphoid over 685 kilobases, making this locus far more complexcells, all leukemias and lymphomas generally share than others. Nevertheless, accurate molecular analysis ofone or more cell-specific or clonal antigen receptor the TRB genes is an important tool for the assessment ofgene rearrangements. Clonality does not always imply clonality in suspected T-cell and some B-cell proliferations,malignancy; all results must be interpreted in the context as TRB gene rearrangements occur not only in almost allof all of the other available diagnostic criteria. Tests that mature T-cell malignancies, but also in about one-third ofdetect TRB clonal rearrangements can be used to help precursor B-acute lymphoblastic leukemias (B-ALL). 1 identify T-cell and certain B-cell malignancies.Lymphoid cells are different from the other somatic cells in the body, as during development the antigen receptor genes in lymphoid cells (including gene segments within the TRB locus), undergo somatic gene rearrangement. 2References1.JE Miller et al., Molecular Genetic Pathology (2013, 2nd ed.) Springer Science & Business Media 302.2.7.13 and 30.2.7.18.2.Tonegawa S (1983) Somatic Generation of Antibody Diversity. Nature 302:575-58130'