Flow cytometric analysis of phenotypes and naïve/memory/effector T-cell subsets of T-cell large granular lymphocytic leukemia

This study investigates T-cell antigen expression and functional subsets in T-cell large granular lymphocytic leukemia (T-LGLL) cells by flow cytometry. The leukemic T-LGLs frequently showed expressions of CD57, dim CD2, CD5 and CD7, and more likely CD16 and HLA-DR, compared with reactive/benign T-LGLs. The leukemic T-LGLs were composed predominantly of CD8+ effector memory with re-acquired CD45RA cells (TEMRA, median: 89.6%), with TEMRA cells in >70% of the T-LGLs in 82% of the cases. A small subset of T-LGLL cases showed predominance of CD8+ naïve cells (TN, 2%), CD8+ effector memory cells (TEM, 4%) and transition states between different functional subsets (10%). In contrast, reactive/benign T-LGLs in the control group showed more variable expression of CD62L and CD45RA and more frequent functional subsets other than TEMRA cells. There is significant overlap between leukemic T-LGLs and reactive/benign T-LGLs in terms of common T-cell antigen expression and naïve/memory/effector T-cell subsets.