HLA-DPA1

HLA-DPA1 Full Name

major histocompatibility complex, class II, DP alpha 1

HLA-DPA1 Introduction

HLA-DPA1 (major histocompatibility complex, class II, DP alpha 1) encodes the alpha chain of an HLA-DP heterodimer, a type of MHC class II cell surface protein that is critical for adaptive immunity. Like other MHC class II molecules, the DP heterodimer is composed of an alpha (DPA1) and a beta (DPB1) chain, both anchored in the cell membrane and expressed predominantly on professional antigen-presenting cells (APCs) such as B lymphocytes, dendritic cells, and macrophages. HLA-DP molecules bind peptides derived from extracellular proteins that have been processed in endocytic compartments and present these peptide antigens to CD4⁺ T helper cells, initiating T-cell-mediated immune responses. The DPA1 gene contains multiple exons encoding the leader peptide, extracellular domains, transmembrane region, and cytoplasmic tail, and its polymorphisms contribute to the diversity of peptide binding specificities across the human population.

Figure 1. HLA-DPA1-mediated antigen presentation and T cell activation signaling pathway.

Functionally, the HLA-DP complex formed by DPA1 and DPB1 plays a central role in antigen processing and presentation pathways. After synthesis in the endoplasmic reticulum, the alpha and beta chains associate with the invariant chain (CD74) and traffic through the endosomal/lysosomal system where foreign protein fragments are loaded into the peptide binding groove. Once high-affinity peptides replace the invariant chain fragment (CLIP), the peptide-loaded MHC class II molecule is transported to the cell surface for recognition by the T-cell receptor on CD4⁺ T cells. This interaction is a pivotal step in triggering helper T-cell activation, cytokine production, and downstream adaptive immune responses necessary for defense against pathogens and for shaping immunological memory. Expression of HLA-DPA1 is enriched in antigen presenting cells and other immune-related tissues, reflecting its role in immune regulation.

Clinically, polymorphisms in HLA-DPA1 and its partnering beta chain HLA-DPB1 have been associated with susceptibility to a variety of diseases and immune-mediated traits. Certain HLA-DPA1/DPB1 haplotypes show statistical associations with autoimmune and inflammatory conditions such as ankylosing spondylitis, where variants in the HLA-DP region contribute to disease risk beyond classic HLA-B27 effects, and primary sclerosing cholangitis through NK cell activation pathways. Variation in HLA-DPA1 has also been linked to differences in response to viral infections like persistent hepatitis B and C, likely reflecting altered antigen presentation efficiency. Moreover, HLA-DP polymorphisms can influence outcomes in transplantation immunology and have relevance for graft rejection and alloreactivity. These disease associations underscore the importance of HLA-DPA1 diversity in shaping immune system interactions with both self and non-self antigens across human populations.

Alternate Names for HLA-DPA1

HLA-DPA1; major histocompatibility complex, class II, DP alpha 1; PLT1; HLADP; HLASB; DP(W3); DP(W4); HLA-DP1A; HLA class II histocompatibility antigen, DP alpha 1 chain; HLA-SB alpha chain; MHC class II antigen; MHC class II DP3-alpha; Primed lymphocyte test-1; MHC class II HLA-DPA1 antigen;

• 1. Shi K, et al.; HLA-DPA1 overexpression inhibits cancer progression, reduces resistance to cisplatin, and correlates with increased immune infiltration in lung adenocarcinoma. Aging (Albany NY). 2023, 15(20):11067-11091.