PRH2 (proline rich protein HaeIII subfamily 2) encodes acidic proline-rich proteins (aPRPs) that are major components of human saliva with diverse biological functions. PRH2 is located on chromosome 12.2 within a cluster of proline-rich protein genes and exists in two commonly occurring allelic variants that code for PRP-1 and PRP-2 proteins 1. The gene products undergo complex post-translational modifications including proteolytic cleavage by convertases and carboxypeptidases, phosphorylation, and various other modifications, generating multiple protein species that contribute significantly to salivary proteome heterogeneity 2. PRH2-encoded proteins appear in saliva around 180 days of postconceptional age during human development 3. Functionally, PRH2 genetic variants serve as receptors for indigenous oral bacteria and play crucial roles in dental caries susceptibility, with different allelic combinations creating distinct phenotypes that influence bacterial adhesion patterns and caries development 45. Additionally, PRH2 has emerged as a potential autoimmune biomarker, with anti-PRH2 autoantibodies identified in Takayasu arteritis patients, showing 88.3% specificity as a diagnostic marker 6. The protein has also been implicated in cancer research as a potential prognostic biomarker for clear cell renal cell carcinoma 7.