We have developed a quantitative assay for tissue-specific adhesive components which is based on the agglutination of glutaraldehyde-fixed cells. At least 2 components are required for fixed-cell agglutination: a cell-surface ligand which is obtained from tissue culture-conditioned medium, and a soluble ‘agglutinin’ which accumulates in conditioned medium from monolayer cultures. Our results suggest that the surface-binding ligand and the agglutinin interact directly, resulting in tissue-specific agglutination of cells. The agglutination reaction exhibits divalent cation, temperature, and pH dependence. Several models of cell adhesion are described; the simplest of these which can account for the data is a multicomponent model in which the 2 adhesive components have structural roles.

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