Cell-cell adhesion in the immune system.

Interactions between cells are essential for function and regulation of the immune system. Some of these interactions are mediated by soluble factors such as immunoglobulins or interleukins, which can serve as chemical messengers that transmit information between widely separated cells. In other cases interaction requires physical contact between the cells and cell-cell adhesion. In this review George Bell emphasizes adhesion mediated by specific cell-surface receptors and/or ligands, including instances in which the receptors have not been identified and are inferred from specificity of interaction rather than biochemical characterization.