There is provided an antagonist of zB7R1 wherein the antagonist inhibits zB7R1-mediated signaling, comprising: (i) a blocking agent that inhibits the interactions between zB7R1 and its counter-receptor； (ii) an antisense oligonucleotide or inhibitory RNA sequence directed to a zB7R1 polynucleotide, wherein the zB7R1 polynucleotide comprises a nucleotide sequence selected from the group consisting of SEQ ID NO: 1 and SEQ ID NO: 5, or a nucleotide sequence that encodes a polypeptide sequence of SEQ ID NO: 2, SEQ ID NO:3, SEQ ID NO: 6 and SEQ ID NO:7； (iii) an antisense oligonucleotide or inhibitory RNA sequence directed to the nucleic acid sequence of the zB7R1 counter-receptor； (iv) a soluble CD155 polypeptide or fusion protein, wherein said soluble CD155 polypeptide or fusion protein has a modified amino acid sequence and is thus incapable of activating zBTR1-mediated signaling, and wherein said soluble CD155 polypeptide or fusion protein inhibits the interaction between zB7R1 and CD155； or (v) a small molecule inhibitor of the interaction between zB7R1 and CD155. There is also provided a soluble zB7R1 polypeptide comprising a sequence of amino acid residues having at least 95% sequence identity with amino acid residues 16-140 of SEQ ID NO:2 or amino acid residues 27-208 of SEQ ID NO: 6 wherein said soluble polypeptide stimulates B7R1 mediated-signaling.
