TCR Vbeta repertoire analysis in CD56+ CD16(dim/-) T-cell large granular lymphocyte leukaemia: association with CD4 single and CD4/CD8 double positive phenotypes.

We report 10 patients with T-cell large granular lymphocyte (LGL) leukaemia: four patients had CD16+ CD56- LGL lymphocytes (typical for LGL leukaemia), and six patients had CD56+ CD16(dim/-) LGL lymphocytes (atypical). Among the CD56+ CD(dim/-) patients, LGL lymphocytes were CD4+ CD8- in one patient, CD4/CD8 double positive (DP) in three, and CD4- CD8+ in two. The CD4+ CD8dim DP cells expressed a CD8alphaalpha homodimer. T-cell receptor (TCR) Vbeta complementarity-determining region 3 (CDR3) size distribution analysis and direct sequencing identified at least 1 in-frame clonal TCR Vbeta transcript in each patient; three patients had two or three different clonal sequences. To determine whether these transcripts were translated into cell surface TCR, we performed flow cytometric analysis using Vbeta monoclonal antibodies (mAbs). A single Vbeta protein was identified in patients, even those with multiple in-frame transcripts. Previous and present results suggest that CD56+ CD16(dim/-) LGL leukaemia is more common than previously thought, and is associated with unusual phenotypes. When assessed using only molecular techniques, the monoclonal status of this disease may be misinterpreted as oligoclonal; thus, flow cytometric analysis using Vbeta mAb is quite useful. Because mAbs do not cover the entire Vbeta repertoire, assessing clonality using a combination of molecular methods and mAbs is preferable.