Gene Information
Gene Symbol
Entrez Gene ID
Gene Name
Major histocompatibility complex, class II, DQ alpha 1
Chromosomal Location
HLA-DQA1 belongs to the HLA class II alpha chain paralogues. The class II molecule is a heterodimer consisting of an alpha (DQA) and a beta chain (DQB), both anchored in the membrane. It plays a central role in the immune system by presenting peptides derived from extracellular proteins. Class II molecules are expressed in antigen presenting cells (APC: B Lymphocytes, dendritic cells, macrophages). The alpha chain is approximately 33-35 kDa. It is encoded by 5 exons; exon 1 encodes the leader peptide, exons 2 and 3 encode the two extracellular domains, and exon 4 encodes the transmembrane domain and the cytoplasmic tail. Within the DQ molecule both the alpha chain and the beta chain contain the polymorphisms specifying the peptide binding specificities, resulting in up to four different molecules. Typing for these polymorphisms is routinely done for bone marrow transplantation. (provided by RefSeq, Jul 2008)
GeneCards ID
RefSeq DNA
RefSeq mRNA

Gene Ontology (GO)

GO ID Ontology Definition Evidence Reference
GO:0006955 Biological process Immune response NAS 3584986
GO:0005887 Cellular component Integral component of plasma membrane NAS 3584986
GO:0032395 Molecular function MHC class II receptor activity TAS 2300572
Protein Information
Protein Name
DQ-A1 , leucocyte antigen DQA1 , GSE , major histocompatibility complex, class II, DQ alpha 1, HLA class II histocompatibility antigen, DQ(W3) alpha chain , HLA class II histocompatibility antigen, DQ alpha 1 chain , MHC class II HLA-D alpha glycoprotein , HLA-DQA , CD , MHC class II antigen , DC-alpha , DC-1 alpha chain , MHC class II HLA-DQ-alpha-1 , MHC HLA-DQ alpha , CELIAC1 , HLA-DCA , MHC class II DQA1 , MHC class II surface glycoprotein , leukocyte antigen alpha chain
Binds peptides derived from antigens that access the endocytic route of antigen presenting cells (APC) and presents them on the cell surface for recognition by the CD4 T-cells. The peptide binding cleft accomodates peptides of 10-30 residues. The peptides presented by MHC class II molecules are generated mostly by degradation of proteins that access the endocytic route, where they are processed by lysosomal proteases and other hydrolases. Exogenous antigens that have been endocytosed by the APC are thus readily available for presentation via MHC II molecules, and for this reason this antigen presentation pathway is usually referred to as exogenous. As membrane proteins on their way to degradation in lysosomes as part of their normal turn-over are also contained in the endosomal/lysosomal compartments, exogenous antigens must compete with those derived from endogenous components. Autophagy is also a source of endogenous peptides, autophagosomes constitutively fuse with MHC class II loading compartments. In addition to APCs, other cells of the gastrointestinal tract, such as epithelial cells, express MHC class II molecules and CD74 and act as APCs, which is an unusual trait of the GI tract. To produce a MHC class II molecule that presents an antigen, three MHC class II molecules (heterodimers of an alpha and a beta chain) associate with a CD74 trimer in the ER to form an heterononamer. Soon after the entry of this complex into the endosomal/lysosomal system where antigen processing occurs, CD74 undergoes a sequential degradation by various proteases, including CTSS and CTSL, leaving a small fragment termed CLIP (class-II-associated invariant chain peptide). The removal of CLIP is facilitated by HLA-DM via direct binding to the alpha-beta-CLIP complex so that CLIP is released. HLA-DM stabilizes MHC class II molecules until primary high affinity antigenic peptides are bound. The MHC II molecule bound to a peptide is then transported to the cell membrane surface. In B-cells, the interaction between HLA-DM and MHC class II molecules is regulated by HLA-DO. Primary dendritic cells (DCs) also to express HLA-DO. Lysosomal miroenvironment has been implicated in the regulation of antigen loading into MHC II molecules, increased acidification produces increased proteolysis and efficient peptide loading
Refseq Proteins
Pfam Accession Pfam ID
PF00993 MHC_II_alpha Class II histocompatibility antigen, alpha domain
PF07654 C1-set Immunoglobulin C1-set domain
Phenotype MIM ID

Associated Diseases

Diseases References
Arthritis juvenile rheumatoid 7652738
Asthma 11953202, 12890388
Autoimmune diseases 9209509, 8995182, 7608264
Diabetes mellitus insulin-dependent 9458118, 10697396, 8820406, 7817375, 8597561, 1347765, 9929871, 7624445
Lupus erythematosus systemic 8406614, 8456439
PMID: 1471701

Increased risk for polycystic ovary syndrome associated with human leukocyte antigen DQA1*0501.

Ober C, Weil S, Steck T, Billstrand C, Levrant S, Barnes R
Department of Obstetrics and Gynecology, Chicago Lying-In Hospital, University of Chicago, IL 60637.
Am J Obstet Gynecol. 1992 Dec;167(6):1803-6.


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