Transendothelial migration of lymphocytes in chronic lymphocytic leukaemia is impaired and involved down‐regulation of both L‐selectin and CD23

Abstract

Summary.Chronic lymphocytic leukaemia (B-CLL) is characterized by a progressive accumulation of B lymphocytes in blood and bone marrow and high concentrations of soluble CD23 and L-selectin are found in the serum of these patients. In this study lymphocytes from normal subjects and patients with B-CLL were allowed to undergo transendothelial migration across confluent layers of human umbilical vein endothelial cells. Lymphocytes in B-CLL samples showed an impaired capacity to migrate while the minor proportion of normal T cells was enriched by a mean of 2·5-fold in the transmigrated lymphocytes. In contrast, the ratio of B to T lymphocytes in normal preparations was unchanged in the transmigrated population. The expression of adhesion molecules on B-CLL lymphocytes before and after transendothelial migration was studied by flow cytometry which showed that 71 Ϯ 5% of L-selectin was lost from the surface of transmigrated lymphocytes. T and B cells from normal subjects also showed a major loss of L-selectin after transmigration. B-CLL lymphocytes and normal B cells expressed CD23 but this molecule was down-regulated following transendothelial migration, whereas the expression of VLA-4, ICAM-1, LFA-1 and CD44 was unchanged. Lymphocytes incubated with oxidized ATP, an irreversible inhibitor of P2Z/P2X7 purinoceptors, retained their capacity for transendothelial migration and showed the same loss of L-selectin as control leukaemic lymphocytes. Our results show that B-CLL lymphocytes have impaired ability for transendothelial migration compared to normal peripheral blood lymphocytes. Moreover, transendothelial migration involves a universal loss of L-selectin and CD23 from lymphocytes which suggests that the high serum levels of soluble L-selectin and CD23 observed in B-CLL may be generated by shedding during the process of transendothelial migration.

P2X7 receptors regulate multiple types of membrane trafficking responses and non-classical secretion pathways

“…The ability of matrix metalloprotease (MMP) inhibitors to markedly suppress P2X7R-dependent loss of surface CD62L from human B cells indicated that bona fide shedding of the ecto-domain is the predominant mechanism. P2X7R activation in human B cells and monocytederived dendritic cells has also been shown to elicit the shedding of CD23, an intrinsic plasma membrane protein that functions as a low-affinity receptor for IgE with links to chronic inflammatory diseases [22,23]. The ATPinduced loss of surface anti-CD23 epitopes was correlated with the extracellular accumulation of soluble CD23 protein which was suppressed in the presence of MMP inhibitors.…”

Ly6C Induces Clustering of LFA-1 (CD11a/CD18) and Is Involved in Subtype-Specific Adhesion of CD8 T Cells

“…5A). Expression of L-selectin, which is shed during transmigration and rapidly gained back in the lymph node after homing (29), among the transferred, labeled T cells was the same before and after the homing to lymph nodes. A comparison of Ly6C expression among the labeled cells that were found in various organs indicated that they homed equally well to lymph nodes, liver, and spleen (Fig.…”

Roles of extracellular nucleotides and P2 receptors in ectodomain shedding

“…In contrast, oxidised ATP did not affect the loss of CD62L during CLL lymphocyte transmigration [69], suggesting P2X7 may not play a role in this process. This difference may be due to different experimental conditions including cell type and species.…”