Methods for upregulating an immune response with agents that inhibit the intereaction between PD-L2 and PD-1

A method for upregulating an immune response comprising contacting an immune cell with an agent that downmodulates the interaction between a PD-L2 polypeptide comprising the amino acid sequence shown in SEQ ID NO:2 and PD-1 to thereby upregulate the immune response, wherein the agent is selected from the group consisting of a blocking antibody that recognizes PD-L2, a combination of a blocking antibody that recognizes PD-L2 and a blocking antibody that recognizes PD-L1, a form of PD-L2 that does not activate PD-1 and a soluble form of PD-1.

A method for upregulating an immune response comprising contacting an immune cell with an agent that downmodulates the interaction between a PD-L2 polypeptide comprising the amino acid sequence shown in SEQ ID NO:5 and PD-1 to thereby modulate the immune response, wherein the agent is selected from the group consisting of:

• a blocking antibody that recognizes PD-L2, a combination of a blocking antibody that recognizes PD-L2 and a blocking antibody that recognizes PD-L1, a form of PD-L2 that does not activate PD-1 and a soluble form of PD-1.

A method for upregulating an immune response, comprising contacting a PD-L2 polypeptide comprising the amino acid sequence shown in SEQ ID NO:

• 5 or a cell expressing the polypeptide with a compound which binds to the polypeptide in a sufficient concentration to downmodulate PD-1 mediated signaling by the polypeptide such that the immune response is upmodulated, wherein the compound is selected from the group consisting of:
• a blocking antibody that recognizes PD-L2, a combination of a blocking antibody that recognizes PD-L2 and a blocking antibody that recognizes PD-L1, a form of PD-L2 that does not activate PD-1, and a soluble form of PD-1.