Regulation of ICAM‐3 (CD50) membrane expression on human neutrophils through a proteolytic shedding mechanism

Abstract

The regulation of the cell surface expression of ICAM-3 (CD50) was investigated in human neutrophils. Immunofluorescence flow cytometry analysis revealed a remarkable and very rapid down-regulation of the ICAM-3 cell surface expression upon neutrophil activation with stimulating agents such as phorbol myristate acetate (PMA) or calcium ionophore. A similar low expression of ICAM-3 was observed on neutrophils from patients undergoing hemodialysis with cell-activating cellulosic membranes. Internalization assays with 125I-labeled anti-ICAM-3 monoclonal antibody (mAb) suggested that ICAM-3-down-regulation was due to antigen release from the cell surface towards the outer milieu, rather than to antigen internalization. Immunoprecipitation studies confirmed this down-regulatory effect, and revealed the presence of ICAM-3 in cell-free supernatants from activated neutrophils. Furthermore, the presence of a soluble form of ICAM-3 with a range of concentrations of 0-296 ng/ml in the plasma from healthy human volunteers was detected by using a two-site mAb radioimmunoassay. A proteolytic mechanism likely accounts for this process since protease inhibitors virtually abrogated the PMA-induced down-regulation of ICAM-3. Functional studies showed that anti-ICAM-3 mAb were able to trigger homotypic neutrophil aggregation both before and after ICAM-3 down-regulation, indicating that the fraction of ICAM-3 molecules remaining on the neutrophil surface upon activation are still capable of sustaining cell adhesion. In contrast, the loss of L-selectin (CD62L) on activated neutrophils was almost complete, thus leading to an impairment of L-selectin-mediated neutrophil-endothelial cell adhesion. These results indicate that ICAM-3 is released to the medium upon neutrophil stimulation and that both ICAM-3 and L-selectin have a role in the neutrophil adhesive phenomena.

Activation of Human Neutrophils by the Pollutant Sodium Sulfite: Effect on Cytokine Production, Chemotaxis, and Cell Surface Expression of Cell Adhesion Molecules

“…Since the expression of different cell surface molecules is modulated by various neutrophil agonists, we decided to verify if Na 2 SO 3 could modulate the expression of the ␤ 2 integrins CD11a, CD11b, and CD11c/ CD18 as well as ICAM-1 (CD54) and ICAM-3 (CD50), known to be expressed and/or induced in human neutrophils (16,17). As illustrated in Fig.…”

The role of ICAM-1 on T-cells in the pathogenesis of asthma

“…Chemokines MIP-1α, MIP-1β, RANTES, and interferon-inducible protein (IP)-10 cause increased in vitro adhesion of both resting and anti-CD3-activated T-cells to recombinant human (rh) ICAM-1 and rhVCAM-1 and to extracellular matrix proteins, and this is accompanied by increased affinity of the integrin molecules [3]. In experimental conditions there is a proteolytic cleavage and shedding of the adhesion molecules redistributed at the level of the cellular uropod [35,36].…”

Physiological activation of human neutrophils down-regulates CD53 cell surface antigen

“…In this context, proteolytic modulation of membrane proteins is becoming an important regulatory mechanism in cell biology. This proteolytic downregulation has been shown on an increasing number of proteins, including some cytokine receptors such as tumor necrosis factor ␣ (TNF-␣) receptor and interleukin-6 (IL-6) receptor [30], Fas ligand [31], adhesion molecules such as L-selectin [32,33], ICAM-3 [34], CD43, and CD44 [35]. Specific proteases are present on the cell surface to specifically activate the thrombin and plasminogen systems [36,37].…”