T Cell Large Granular Lymphocyte (T-LGL) Lymphoproliferative Disorders are a heterogeneous group of uncommon diseases which may involve a polyclonal or a monoclonal T cell population, which bear characteristic surface markers corresponding to activated cytotoxic (CD3+, CD8+) lymphocytes. They are often associated with quite severe neutropenia, anemia, and thrombocytopenia which may be life-threatening. There is some evidence that the abnormal cytotoxic lymphocyte population may cause the cytopenias by suppressing hematopoiesis, although the mechanism is unclear. Case reports suggest that immunosuppressive therapy directed toward T cells may reverse the cytopenia. This pilot study involving up to 25 patients evaluates the clinical response to cyclosporine, an immunosuppressive drug, and seeks to elucidate the mechanism underlying the cytopenia.