Test Details: Human leukocyte antigens (HLA) are proteins that help the body's immune system distinguish between its own cells and foreign, harmful substances. This test detects HLA-B27 on the surface of T cells. The most widely used diagnostic method of HLA-B27 determination is the flow cytometry assay. In this assay, HLA-B27 present on the T cell surface is detected using a specific monoclonal antibody. HLA-B27 can also be detected by PCR. If you have HLA-B27, you may have an autoimmune disease called akyloting spondilysis. An autoimmune disease is when your immune system attacks your own cells.