Impaired transendothelial migration of B-CLL lymphocytes: a defect linked to low L-selectin expression

The emigration of lymphocytes from blood into lymph nodes is regulated by t he expression of the adhesion molecule, L-selectin on the lymphocyte surfac e which arrests the rolling of the cell on the vessel wall and allows firme r adhesive interactions to develop. The expression of L-selectin on B-CLL l ymphocytes is less than half that on normal lymphocytes and this difference correlates with an impaired capacity of B-CLL lymphocytes to migrate benea th a monolayer of human umbilical vein endothelial cells. Both the B-cell a nd T-cell lymphocytes from normal subjects and B-CLL patients show down-reg ulation of L-selectin and CD23 after transendothelial migration. The reduce d expression of L-selectin on B-CLL lymphocytes leads to a relative "trappi ng" of these cells in the vascular space and is one factor contributing to the elevation of peripheral lymphocyte count.