Expression of the mid-stage differentiation B-cell antigen GP-70 in patients with early and stable form of B-CLL

Abstract

The expression of B-cell surface markers SmIg and GP-70 was determined on the mononuclear cells from the peripheral blood of 25 patients with chronic lymphocytic leukemia (CLL), 10 patients with multiple myeloma (MM), 6 normal blood donors and in 3 cases of unexplained persistent lymphocytosis. GP-70 was expressed only in CLL patients whereas multiple myeloma patients, blood donors and patients with unexplained lymphocytosis were all negative to GP-70. SmIg was expressed in CLL patients and in some of the multiple myeloma patients. Subgrouping of CLL patients to "early", stable patients (10) and to more advanced CLL patients (15) revealed differential expression of GP-70 on CLL cells from patients with more advanced stage of disease rather than in the patients with the "early" stable clinical course of disease. SmIg, on the other hand, was expressed equally on both subgroups of CLL. Furthermore, in some cases (25%) where SmIg and the light chains of Ig were only weakly expressed or were absent, GP-70 was markedly expressed. These findings suggest that GP-70 can be used as a single laboratory determination to establish clonality of the B-lymphocyte proliferation in CLL. In addition, expression of GP-70 correlates with significant clinical parameters of the disease.