Abstract: The present disclosure relates to SH3YL1 monoclonal antibodies and compositions comprising the SH3YL1 monoclonal antibodies. The disclosure also relates to isolated nucleic acid molecules encoding the SH3YL1 antibodies, vectors comprising the nucleic acid molecules, and host cells comprising the vectors. Also disclosed are methods of modulating an immune response, methods of treating diabetic nephropathy, and methods of treating non-alcoholic steatosis hepatitis comprising administering the SH3YL1 antibodies. Also disclosed are methods of treating acute kidney injury and methods of treating inflammatory bowel disease comprising administering the SH3YL1 antibodies.