Changes in adhesion molecule expression and function in B-cell chronic lymphocytic leukaemia after in vitro interferon-alpha stimulation.

Peripheral blood mononuclear cells (PBMCs) from 10 B-CLL patients were investigated after 24 hours of in vitro interferon-alpha (IFN-alpha) stimulation. The constitutional expression of the L-selectins (LECAM-1), LFA-1/CD11a, VLA alpha-4/CDw49d and ICAM-1/CD54 adhesion molecules was detected, and changes in their density after IFN-alpha stimulation were compared to results obtained by the high endothelial venule (HEV)-binding assay and a carbohydrate (phosphonomannan core polysaccharide: PPME and fucoidin) immobilization test. The LECAM-1 and ICAM-1 molecules were expressed on the great majority of CLL cells, while the LFA-1 and VLA-4 alpha-chains were expressed by only a small number of cells. Statistically significant changes (p < 0.001) were observed in LECAM-1 antigen density (changes in mean cell fluorescence), as well as in functional tests (HEV-, PPME- and fucoidin-binding; p < 0.01) after in vitro IFN-alpha stimulation. Based on a prior study (Jewell et al., Leukemia 1992: 6: 400-404) and on the present findings, not only an increased expression but also an enhanced function of the L-selectins seem to be well substantiated after IFN-alpha stimulation, which may explain the therapeutic effect of IFN-alpha in reducing the accumulation of leukaemic B cells in the blood. The remarkably high expression of ICAM-1 in this series necessitates further studies to clarify the exact expression rate and role of this molecule.