Chronic lymphocytic leukaemia: Clonal origin in a committed B-lymphocyte progenitor.

The glucose-6-phosphate dehydrogenase (G.-6-P.D.) types of isolated blood-cell populations and normal skin were determined in two patients with chronic lymphocytic leukaemia (C.L.L.) who were heterozygous at the G.-6-P.D. locus. Normal tissues from each patient manifested both A and B G.-6-P.D. types, but the C.L.L. B-lymphocyte preparation from one patient showed only a single enzyme type, and from the other patient it showed 95% activity of one G.-6-P.D. type. These observations confirm the supposition based on immunoglobulin-marker data that at the time of study C.L.L. has a clonal origin. In contrast to the B lymphocytes, granulocytes, erythrocytes, platelets, and T lymphocytes displayed both enzyme types in proportions similar to those found in skin. These findings indicate that C.L.L. involves committed B-lymphocyte progenitors. Thus, the disease stands in contrast to chronic myelocytic leukaemia and other myeloproliferative syndromes, all of which involve multipotent haemopoietic stem cells.