CPN2 (carboxypeptidase N subunit 2) is an 83 kDa regulatory subunit that stabilizes and maintains circulating carboxypeptidase N (CPN), a plasma zinc metalloprotease 1. CPN2 protects the catalytic subunit (CPN1) from degradation at physiological temperature and may function as an allosteric modulator. The CPN complex cleaves C-terminal arginines and lysines from inflammatory mediators including complement anaphylatoxins and kinins, thereby modulating their biological activity 1. CPN2 exhibits immunoregulatory function by suppressing NF-κB pathway activation and reducing inflammatory cytokine production 2. In cryptorchidism models, CPN2 overexpression preserved spermatogonial stem cell proliferation and reduced apoptosis by inhibiting plasma cell infiltration 2. Genetic studies identified CPN2 as a causal factor influencing myasthenia gravis susceptibility through protein quantitative trait loci (pQTL) mechanisms 3. CPN2 serves as a disease biomarker across multiple conditions. Altered CPN2 expression appears in hepatocellular carcinoma serum extracellular vesicles 4, type 1 diabetes 5, and canine chr3 inflammatory enteropathies where CPN2 downregulation correlates with disease remission 6. Additionally, CPN2 shows differential regulation in protein S deficiency-associated coagulopathy 7 and Sézary syndrome through novel fusion transcripts 8. These findings establish CPN2 as a pleiotropic regulator of inflammation and immune responses with diagnostic and therapeutic potential.