Differentiation ability of the CLL lymphocyte: an immature lymphocyte or an abnormal leukemic cell?

The present study is concerned with the patterns of cell differentiation in chronic lymphocytic leukemia. Most cases correspond to the proliferation of a B-cell clone. In contrast to the normal B-lymphocyte, the B-cell CLL lymphocyte is characterized by: (1) very low amounts of monoclonal surface Ig; (2) the presence of receptors for mouse red blood cells; (3) the presence in a high percentage of cases of dual B and T markers. T-cell CLL is a rare event and is defined by a peculiar clinical and hematological picture including the presence of receptors for sheep erythrocytes, the reactivity with anti-T sera, and negative or very low values of terminal transferase. Different studies have conflicted in their findings on the incidence of null-cell CLL; however, these cases appear to be rare. Perhaps more sensitive methods of study must be employed before concluding that the null-cell CLL exists and before establishing its incidence. Even though great progress has been made in the understanding of this disease, two main questions remain unresolved: 1. Does the proliferating clone correspond to an immature B-lymphocyte, or does it merely represent an abnormal leukemic cell? 2. What is the role of T cells in B-cell CLL?