CHRONIC LYMPHOCYTIC-LEUKEMIA - THE NATURE OF THE LEUKEMIC-CELL

Far from being the boring, inactive, inert lymphocyte that haematologi sts of old perceived it to be, the chronic lymphocytic leukaemia (CLL) cell has set us many complex problems. The cell is apparently stuck i n G(0) in cell cycle, yet expresses many activation markers. The cells apparently manufacture many cytokines and respond in vitro to even mo re, yet cells entering even G(1) are few. The cell surface marker prof ile is unique. There is apparently no normal equivalent of the CLL cel l. In part, this may be because the cell is malignant; malignant cells often express aberrant markers. Consistent chromosomal abnormalities are emerging but we have no idea how these abnormalities translate int o molecular mistakes that dictate the peculiar nature of the cell. CLL cells carry a characteristic set of adhesion molecules, but we cannot read their homing and recycling instructions. The outstanding irregul arities of the CLL cell are its CD5 positivity and its sparse surface immunoglobulin. This ought to translate as an anergic B1 cell, perhaps programmed for autoimmunity. If the tumour cell were responsible for the patient's production of immunoglobulin or secretion of autoantibod ies, then a pattern might have emerged. Alas, these are the product of the normal B cells. How the CLL cell induces these complications is u nknown. Thus, despite the information contained in this review, the CL L cell remains a puzzle.