What immunological marker is frequently associated with ankylosing spondylitis?

Ankylosing spondylitis is strongly associated with the presence of HLA-B27, which is a cell surface antigen found on the surface of certain immune cells. The association of HLA-B27 with ankylosing spondylitis is one of the most well-established connections between a specific HLA (human leukocyte antigen) type and an autoimmune condition.

The mechanism behind this association is not completely understood, but it is believed that individuals who express HLA-B27 may have an enhanced immune response that contributes to the development of spondyloarthritis. Studies have shown that up to 90% of individuals with ankylosing spondylitis carry this antigen, which is significantly higher compared to the general population where the prevalence of HLA-B27 is about 6-8%.

Other HLA types listed, such as HLA-DR4 and HLA-DQ2, are associated with different autoimmune diseases, such as rheumatoid arthritis and celiac disease, respectively. HLA-A1 has not been implicated in ankylosing spondylitis. Therefore, the specificity of HLA-B27 for ankylosing spondylitis is a critical factor in its diagnosis and an important aspect of understanding the immunological