Our immune system does an awesome job (most of the time) of fighting off pathogenic bacteria and viruses. But to fight off these pathogens, the body needs to know that they are the bad guys. This is where the HLA system comes in.
Human leukocyte antigens (HLA) is the part of our immune system known as the major histocompatibility complex. The HLA genes code for the proteins that help our body determine what is a foreign invader that needs to be attacked.
There are many different HLA serotypes that people can have, giving us all slightly different strengths and weaknesses against microbial diseases. But along with attacking foreign invaders, a handful of HLA types also increase the susceptibility to autoimmune diseases, where the body attacks its own cells.
HLA-B27 is linked to susceptibility to inflammatory related autoimmune diseases including:
Ankylosing spondylitis is a chronic inflammatory disease that mainly affects the spine. It causes back pain and spinal stiffness, and the vertebrae can fuse together. More info can be found on the Spondylitis Association of America site. Carriers of HLA-B27 are at a 20-fold risk for the disease.
Genetic variants included in 23 and Me data that code for HLA-B27 are listed below. These variants show if you are likely to carry an HLA-B27 type. But there are several subtypes of HLA-B27 and not all of them cause a higher risk of inflammatory autoimmune diseases. A blood test is still necessary to be 100% certain that you carry the HLA-B27 type associated with autoimmune diseases.
Check your genetic data for rs4349859 (23andMe v5 only; AncestryDNA):
Check your genetic data for rs13202464 (23andMe v4, v5; AncestryDNA):
Don’t freak out if you are a carrier of HLA-B27 — certain population groups have up to 20% of people carrying these variants. In Caucasians, about 10% of people carry one copy, whereas only 1% of African populations carry HLA-B27.[ref]
Although HLA-B27 increases the risk of ankylosing spondylosis by 20-fold, it is still a rare disease with about 1 in 2000 people having it.[ref] If you have the HLA-B27 serotype, the lifetime absolute risk is about 6%.[ref] There are other genetic variants thought to be involved in the risk for ankylosing spondylosis, as well environmental factors.[ref]
Survival advantage: Interestingly, carriers of the HLA-B27 have a survival advantage for HIV and hepatitis C.[ref]
Gut Microbiome: There is also a connection between HLA-B27 and changes to the gut microbiome.[ref] Spondylitis patients also showed changes in the gut microbiome with decreased F. prausnitzii and increased Bacteroides fragilis.[ref] You may want to get a gut microbiome test done to see if everything is in order down there.
Probiotics: Animal studies show that Lactobacillus G/G probiotics may help with preventing recurrence of inflammatory bowel problems associated with HLA-B27.[ref] Although I couldn’t find a human clinical trial on it, if you are wanting to try a Lactobacillus G/G probiotic, Culturelle contains that strain.
AIP diet: The link between diet and symptoms of reactive arthritis or ankylosing spondylitis isn’t clear. A meta-study looked at a bunch of studies on the subject and found no statistical links with diet. But individuals report that diet can make a difference in their joint pain with certain foods making it worse. So trying an elimination diet or the autoimmune protocol diet may be worthwhile.