The present invention relates to the discovery, identification, and characterization of novel genes encoding proteins that play a role in immune system development and function, collectively termed Nessie. The invention encompasses the described polynucleotides, the encoded proteins, fusion proteins, polypeptides and peptides, genetically engineered animals that either under- or over-express the disclosed sequences, antibodies to the encoded proteins and peptides, host cell expression systems, antagonists and agonists of the proteins, and other compounds that modulate the expression or activity of the proteins encoded by the disclosed sequences that can be used for diagnosis, drug screening, clinical trial monitoring and the treatment of diseases and disorders.