HLA-B27 is a human leukocyte antigen that helps the body differentiate its own cells from foreign substances. A test indicating that HLA-B27 is present means that the patient might have a risk of developing an autoimmune disorder, notes MedlinePlus.
Human leukocyte antigens help regulate the immune system, and their main role is to let the body tell the difference between normal cells and substances that it needs to attack, states MedlinePlus. Patients may get an HLA-B27 antigen test to find the cause of joint swelling and pain. Another reason for an HLA test is to see whether or not the patient can donate organs or bone marrow to another person.
A normal test result for a patient is a negative result that says no HLA-B27 is present. A positive result means there is more HLA-B27 in the blood than there should be. Conditions such as arthritis, ankylosing spondylitis and inflammation of the sacroiliac joint may cause an increase in HLA-B27 and human leukocyte antigens, states MedlinePlus.
HLA-B27 in the blood may indicate an autoimmune disorder. Typically, people of primarily Caucasian heritage have a naturally higher level of HLA-B27, notes MedlinePlus. The presence of the antigen does not necessarily always indicate a medical problem.