Function and expression of adhesion molecules on human basophils

Although the human basophil is predominantly a circulating cell, it is known to participate in a variety of inflammatory responses. For example, basophils have clearly been identified in skin at sites of contact hypersensitivity, erythema multiforme, bullous pemphigoid, and cutaneous basophil hypersensitivity reactions and in the airways of subjects with allergic rhinitis and asthma. In addition, an influx of basophils accompanies the allergic late phase response that occurs after antigen challenge of the skin and airways. Thus basophils, like other granulocytes, can emigrate from the intravascular compartment into specific tissues. The observation that increased numbers of basophils accumulate at certain inflammatory sites suggests that they are activated and recruited to these locations. During this process it is necessary for these cells to interact with endothelial cells, parenchymal cells, and extracellular matrix proteins as they undergo margination, transendothelial migration, and enter the tissue space. Essentially all of the steps in this process involve the interaction of basophil cell surface adhesion molecules with specific adhesion molecule counter-receptors. Several extensive reviews have recently been written on cell adhesion molecule biology and the potential role of these molecules in allergic diseases. This article will focus on the expression and function of adhesion molecules on human basophils.