HLA-B27 is a blood test to look for a protein that is found on the surface of white blood cells. The protein is called human leukocyte antigen B27 (HLA-B27). Human leukocyte antigens (HLAs) are proteins that help the body's immune system tell the difference between its own cells and foreign, harmful substances.
Is HLA-B27 a blood disorder?
The presence of HLA-B27 on your white blood cells can cause your immune system to attack those otherwise healthy cells. When this occurs, it can result in an autoimmune disease or immune-mediated disease, such as juvenile rheumatoid arthritis or ankylosing spondylitis.