Isolation of a clone encoding the mouse lymph node homing receptor reveals a deduced protein with an unusual protein mosaic architecture, containing a separate carbohydrate-binding (lectin) domain, an epidermal growth factor-like (EGF) domain, and an extracellular precisely duplicated repeat unit, which preserves the motif seen in the homologous repeat structure of complement regulatory proteins and other proteins. The receptor molecule is potentially highly glycosylated, and contains an apparent transmembrane region. Analysis of messenger RNA transcripts reveals a predominantly lymphoid distribution in direct relation to the cell surface expression of the MEL-14 determinant, and the cDNA clone is shown to confer the MEL-14 epitope in heterologous cells. The many novel features, including ubiquitination, embodied in this single receptor molecule form the basis for numerous approaches to the study of cell-cell interactions.