T cell variant of chronic lymphocytic leukaemia with chromosome abnormality and defective response to mitogens.

Lymphocytes from a patient with chronic lymphocytic leukaemia, in whom therapy was ineffective, were defined as thymus-derived (T) cells by membrane markers (sheep erythrocyte rosettes, complement rosettes, surface immunoglobulin). The lymphocytes responded weakly to two mitogens, phytohaemagglutinin and the calcium ionophore A23187, but not to concanavalin A. Cytogenetic studies of leukaemic cells from unstimulated and mitogen-stimulated cultures revealed an abnormal karyotype with 45 chromosomes and multiple rearrangements. The T cell variant of classical chronic lymphocytic leukaemia is relatively rare; additional reports are needed to determine if the clinical course is typically less benign than in the common B cell variety, or whether this patient simply represented a late, unresponsive phase of the disease.