Chronic lymphocytic leukaemia of T cell origin. Clinical variation possibly due to involvement of different T lymphocyte subpopulations.

Based on the literature and 2 patients studied, we suggest that at least 2 different clinical entities are included in the concept of T CLL: (i) a clinical variant characterized by a relatively benign course, splenomegaly without lymphadenopathy, low lymphocyte count and granulocytopenia; the proliferating lymphocyte is morphologically mature, of medium size and a cytoplasm with azurophilic granules staining positively for acid phosphatase and corresponding to parallel tubular arrays as demonstrated by electron microscopy. The cells form E-rosettes, have no surface-membrane-bound Ig, but Fc-receptors for IgG. With monoclonal antibodies, the phenotype is OKT3+, OKT4- and OKT8+, theoretically corresponding to the suppressor/cytotoxic T lymphocyte subset, but functionally the cells demonstrate killer cell (responsible for ADCC), but not natural or suppressor cell activity. (ii) another clinical variant with an aggressive course, massive hepato-splenomegaly, lymph node enlargement and very high lymphocyte counts; the lymphocytes are small without cytoplasmic granules; their immunological and functional characteristics have not been determined, but morphologically the cells correspond to the T helper/inducer lymphocyte subset. Thus, involvement of different T lymphocyte subsets may be the reason for the clinical variation in T CLL.