Improvement of extrathymic T cell type of large granular lymphocyte (LGL) leukemia by cyclosporin A: the serum level of Fas ligand is a marker of LGL leukemia activity

: We report a case of γδ T-cell-type large granular lymphocyte (LGL) leukemia (CD3+,CD8+, CD57+,TCR γδ+), which was accompanied by pure red cell aplasia, neutropenia and thrombocytosis. Southern blotting analysis of the T-cell receptor β gene showed the germline configuration, but clonal TCR J γ rearrangements were identified. These granular lymphocytes demonstrated non-major histocompatibility complex-restricted cytotoxicitity. The serum-soluble FasL (sFasL) concentration of this patient was very high, whereas the serum levels of tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), interleukin-1 beta (IL-1β), interleukin-2 (IL-2) and thrombopoietin were normal. After treatment with cyclosporin A, anemia and thrombocytosis were improved, and LGL and the elevated sFasL concentration decreased. These observations suggested that FasL may have played a role in the establishment of the clinical symptoms of this patient and could be useful as an indicator of disease activity.