Generally, this technique is available only in centers that specialize in organ and bone marrow transplantation. In addition to the transplantation, these techniques are used for familial genetic studies as well as for specific disease states. One example is the identification HLA B27 , which is highly associated with ankylosing spondylitis, and as the research continues one can expect that other genetic MHC markers will be identified in particular disease states. The converse is also true. It is now known that certain MHC antigens confer resistance to a given disease, while others confer susceptibility. A word of caution is warranted. These markers only suggest a susceptibility to the disease. Most disease states appear to be polygenic, and factors such as the environtment and past exposure to a given microbe also play a part in establishing the full disease pattern.