HLA-DQB1 is a major histocompatibility complex class II beta chain that functions as a critical antigen-presenting molecule. It forms heterodimeric complexes with HLA-DQA1 alpha chains to present exogenous peptide antigens (10-30 residues) to CD4+ T cells, initiating adaptive immune responses [PMID:UniProt annotation]. The protein binds peptides from endocytosed antigens in acidified endosomal/lysosomal compartments, where CD74-associated invariant chains are proteolytically removed by CTSS/CTSL proteases, followed by HLA-DM-mediated CLIP peptide exchange to facilitate high-affinity antigenic peptide loading. Clinically, HLA-DQB1 polymorphisms show significant disease associations. The DQB1*0602 allele demonstrates tight association with narcolepsy-cataplexy, suggesting autoimmune etiology 1. Regarding cervical cancer, meta-analysis of 4,862 cases identified protective alleles (DQB1*02, *03, *0603) and risk alleles (DQB1*05, *0301, *0402) based on HPV immunologic control 2. HLA-DQB1*02:01 carrier status correlates with reduced serum IgA levels in immunodeficiency patients 3. In systemic lupus erythematosus, DQB1*02 and *06 confer increased disease risk, while DQB1*03 shows protective effects 4. Additionally, HLA-DQB1*02 allele presence increases suicidal behavior risk 5. These associations demonstrate HLA-DQB1's central role in immunological disease susceptibility and immune regulation.