HLA-DRB5 is a human leukocyte antigen (HLA) class II molecule encoded by the HLA-DRB5 gene, part of the HLA-DR gene cluster on chromosome 6. As a component of the major histocompatibility complex (MHC), it plays a critical role in antigen presentation to CD4+ T cells, enabling adaptive immune responses. HLA-DRB5 is expressed primarily in antigen-presenting cells (e.g., dendritic cells, B cells) and exhibits limited polymorphism compared to HLA-DRB1. though its expression is tightly linked to specific HLA-DR haplotypes, such as DRB1*15 and DRB1*16.
Antibodies targeting HLA-DRB5 are typically studied in autoimmune diseases and transplantation. In autoimmune contexts, anti-HLA-DRB5 antibodies may contribute to pathogenic immune responses, particularly in diseases like multiple sclerosis (MS), where the DRB1*15:01-DRB5*01:01 haplotype is a well-established genetic risk factor. These antibodies may arise due to molecular mimicry or epitope spreading, though their exact role in disease progression remains under investigation.
In transplantation, HLA-DRB5 antibodies are monitored for their potential to trigger graft rejection, as mismatched HLA molecules can provoke alloimmune responses. Detection methods include Luminex-based assays and ELISA. Research also explores HLA-DRB5-specific monoclonal antibodies as tools to dissect antigen presentation mechanisms or develop targeted therapies. Despite its lesser-known profile compared to HLA-DRB1. HLA-DRB5 remains a focus in immunogenetics and precision medicine.