CD155 is a member of the immunoglobulin superfamily also known as the human receptor for poliovirus (PVR). Transmembrane glycoproteins related to CD155, the nectins, are well-characterized cell adhesion receptors displaying a high degree of sequence conservation across species. In contrast, CD155 belongs to the category of rapidly evolving genes wherefore a mouse CD155 gene distinguished by an affirmative extent of amino acid conservation as observed for nectins is absent. Consequently, the existing genetic evidence by itself is an inferior indicator to consider whether Tage4, a mouse orphan receptor, represents the murine orthologue of CD155. In the present study Tage4 cDNA was cloned from mouse lung and further characterized genetically. CD155 and Tage4 possess an identical genomic organization and reside in syntenic chromosomal regions. The Tage4 expression pattern was explored applying a newly generated antibody. Both receptors, CD155 in human and Tage4 in mouse, are expressed by intestinal epithelia as well as by follicle associated epithelium and follicular dendritic cells inside Peyer's patches of the gut associated lymphoid tissue. Furthermore, Tage4 lacks self-adhesion capacity but binds to vitronectin, two known features of CD155. These data indicate that Tage4 represents the functional orthologue of CD155 in mouse. Therefore, we suggest to rename Tage4 into rodent CD155. (C) 2003 Elsevier Inc. All rights reserved.