Interactions with cell adhesion molecules determine the organization of tissues and mediate precise cell migrations during embryonic development, inflammation, the immune response, and wound repair (1 –6 ). They are involved in the regulation of gene expression, growth, and differentiation, and are central to invasion and metastasis in cancer (7 –13 ). Viral and bacterial pathogens may also use these molecules to selectively gain entrance to specific cells or tissues (14 –16 ).