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

The capacity of inflammatory cells to adhere is critical to inflammatory responses and involves an array of adhesion molecules grouped into distinct families. Intercellular adhesion molecule (ICAM)-1 has recently attracted much interest in view of increasing evidence that it plays a prominent role in allergic diseases such as asthma and rhinitis. Apart from its role in adhesion of inflammatory cells to vascular endothelium, the extracellular matrix and epithelium, ICAM-1 mediates T-cell/T-cell, T-cell/target cell and T-cell/B-cell interactions. ICAM-1 on the surface of T-cells is thought to participate in signal transduction and may thus modulate several functions including activation, proliferation, cytotoxicity and cytokine production. Because ICAM-1 is the receptor for the major group of rhinoviruses, the most important cause of acute asthma attacks, binding of rhinovirus (RV) to ICAM-1 on T-cells may, at least theoretically, modulate their function. We review here the role of ICAM-1 in asthma and focus more specifically on its expression on T-cells. We present evidence for a general increase in ICAM-1 expression in this disease including recent observations of enhanced expression on the surface of T-cells in the airways lumen. Whilst the implications of intercellular adhesion molecule- upregulation in asthma remain to be fully elucidated, its participation in cell trafficking and activation are being considered as a target for treatment. We present here early attempts to interfere with intercellular adhesion molecule-1 as an adhesion molecule involved in cell influx and studies aimed preventing virus-induced exacerbations of asthma in children based on the knowledge that intercellular adhesion molecule-1 is the receptor for rhinoviruses.