Immunophenotypic analysis of the TCR-V beta repertoire in 98 persistent expansions of CD3(+)/TCR-alpha beta(+) large granular lymphocytes - Utility in assessing clonality and insights into the pathogenesis of the disease

At present, a major challenge in the initial diagnosis of leukemia of large granular lymphocytes (LGLs) is to establish the clonal nature of the expan ded population. in the present study we have analyzed by flow cytometry imm unophenotyping the TCR-V beta repertoire of 98 consecutive cases of persist ent expansions of CD4(+) or CD8(+bright)CD3(+)/TCR-alpha beta (+) LGLs and compared the results with those obtained in molecular studies of TCR-beta g ene rearrangements. Fifty-eight cases were considered to be monoclonal in m olecular studies whereas in the remaining 40 cases there was no evidence fo r monoclonality (11 cases were considered oligoclonal and 29 polyclonal). T he TCR-V beta repertoire was biased to the preferential use of one or more TCR-V beta families in 96% of cases, a total of 124 TCR-V beta expansions b eing diagnosed: one TCR-V beta expansion in 71 cases and two or more TCR-V beta expansions in 23 cases. The highest TCR-V beta expansion observed in e ach case was higher among monoclonal (74 +/- 19%) as compared to nonmonoclo nal cases (24 +/- 14%) (P = 0.001), as did the fraction of LGLs that exhibi ted a TCR-V beta -restricted pattern (86 +/- 16% and 42 +/- 23%, respective ly; P = 0.0001); by contrast, the proportion of cases displaying more than one TCR-V beta expansion was higher in the latter group: 7% versus 48%, res pectively (P = 0.001). Results obtained in oligoclonal cases were intermedi ate between those obtained in polyclonal and monoclonal cases and similar r esults were observed for CD4(+) as for CD8(+bright) T-cell expansions. TCR- V beta families expressed in CD8(+bright) T-cell-LGL proliferations showed a pattern of distribution that mimics the frequency at which the individual TCR-V beta families are represented in normal peripheral blood T cells. As suming that a given proliferation of LGLs is monoclonal whenever there is a n expansion of a given TCR-V beta family of at least 40% of the total CD4() or CD8(+bright) T-cell. compartment, we were able to predict clonality wi th a sensitivity of 93% and a specificity of 80%. By increasing the cut-off value to 60%, sensitivity and specificity were of 81% and 100%. In summary , our results suggest that flow cytometry immunophenotypic analysis of the TCR-V beta repertoire is a powerful screening toot for the assessment of T- cell clonality in persistent expansions of TCR-alpha beta (+) LGLs.