Adhesion molecule expression on B-cell chronic lymphocytic leukemia cells: Malignant cell phenotypes define distinct disease subsets

Expression of surface adhesion molecules of the Ig super-family (CD54 and CD58), of the integrin family (β₁, β₂, and β₃ chains), of the selectin family (L-selectin), and of the lymphocyte homing receptor (CD44) was analyzed on B-cell chronic lymphocytic leukemia (B-CLL) cells from 74 patients. The aim of the study was the definition of phenotypically distinct disease subsets and the correlation of adhesion molecule phenotypes with clinical parameters. Expression of CD58 on B-CLL cells defined more advanced disease stages. In comparison with β chain-positive cases, patients whose cells did not express β₁, β₂, and β₃ integrin chains fell into the most favorable prognostic group, with lower lymphocytosis and the absence of splenomegaly, diffuse bone marrow infiltration, and therapy requirement. A novel finding was the expression of β₃ chains on cells from a minority (12 of 74) of B-CLL cases. β₃ chains were always coexpressed with β₁, and β₂ chains. Two-color immunofluorescence analyses of adhesion molecules such as α_×β₂ integrin (LeuM5) and L-selectin (Leu8) showed that these markers were detectable on variable proportions of leukemic cells, thus confirming the intraclonal phenotypic heterogeneity of B-CLL. Differences in the intensity of CD44 expression were also shown among the various B-CLL clones. Finally, no major variations were shown by comparison of adhesion molecule phenotypes of leukemic cells simultaneously obtained from blood and bone marrow, and of CD5⁺ versus CD5^- clones.