HLA-B27: Genetic Variants That Increase Susceptibility to Autoimmune Diseases

HLA-B27 - check your 23andMe or AncestryDNA

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.

What is the HLA system?

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[ref]
  • reactive arthritis
  • psoriasis
  • inflammatory bowel disease[ref]

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:

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):

  • A/A: high likelihood of carrying 2 copies of HLA-B27[ref][ref][ref]
  • A/G: high likelihood of carrying 1 copy of HLA-B27
  • G/G: normal

Check your genetic data for rs13202464 (23andMe v4, v5; AncestryDNA):

  • G/G: high likelihood of carrying 2 copies of HLA-B27[ref][ref][ref]
  • A/G: high likelihood of carrying 1 copy of HLA-B27
  • A/A: normal


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]

If you want to get the blood test for HLA-B27 and you can’t get it through your doctor, you can order it on your own in the US. UltaLab Tests is one place that I use. There are other websites as well, so shop around for the best price.

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 as 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.

Reactive Arthritis: If you carry the HLA-B27 type and also have reactive arthritis, there is an interesting tie to salmonella persistence or other microbial infections.

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.

More to read:

Autoimmune Disease Genetic Risk Factors: CTLA-4 Gene

How to check your genetic data for celiac genes

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18 Comments on “HLA-B27: Genetic Variants That Increase Susceptibility to Autoimmune Diseases

  1. Thank you! Does anyone know why my results for rs4349859 on 23andme say “not genotyped?” :(

  2. If your results showed one variant saying high likelihood of 1 hla-b27 and the other variant says high likelihood of 2 hla-b27’s the chances are pretty likely right? I’ve been having a lot of joint pain in the last year or two (I’ve had joint issues my whole life but it’s gotten worse after my 2nd child was born) and I started looking more closely at this stuff. It’s very interesting. I think it might be time to find a specialist.

    • Yes, your chances are pretty good that you carry at least one copy of HLA-B27 — but you really should get a blood test done to know for sure. Good luck in getting to the bottom of your joint pain issues :-)

  3. Will having a positive HLA B27 factor prevent you from working in medical laboratory research?

    • I can’t imagine that it would. Plus, employers in the US can’t discriminate based on your genetics.

      • Thank you. I ask because I was told you could not have a compromised immune system. Does having hla b27 make your over all immune system weak or does it only affect the joints?

        • HLA-B27 may actually cause your immune system to be more robust. That is mentioned in the article. All of the impacts of having HLA-B27 are still being studied. I was diagnosed years ago when it was believed that ankylosing spondylitis was the only disease connection but I find new information every few years.

    • Thanks for adding this, Maggie. Do you know anything about the company? What are they doing with the genetic data that you upload? Are they keeping it and using it for either research or marketing purposes?

      • They ask you if you want to save your DNA for future testing. If you didn’t say “yes” to that, I assume they didn’t keep it.

    • Hi Maggie,
      I went to the website you mentioned and uploaded mine. I’m uncertain as to how to interpret the results.
      Searched online and now I’m even more confused.
      Can you guide me?
      Thanks in advance!

  4. I’m a certified functional genetic analyst and was looking at an article about the Chinese using CRISPR to change the HLA-B27 gene to “HIV-resistant” genes. The article failed to mention what you’ve written about here. (The part I find most interesting is the role of the gut microbiome and its relationship to HLA-B27 and expression of disease.) Does anyone else out there see the fairy tale (lie) fed to the public that genes are destiny and all you need to do is cut and paste your way to health?

  5. Hello my results indicated 1 copy HLA B27 but rheumatologist results from 2015 are negative. I do have psoriatic arthritis. Could it switch from inactive to active?

    • Hi Laurel,
      The rheumatologist’s test is more accurate than the DNA on HLA B27. It is unlikely that your DNA changed. The DNA results for the HLA-B27 is not 100% accurate but rather shows whether you are ‘likely’ or not to carry serotype.
      Thanks for asking the question. I’m going to go back and edit the article so that it is more clear in the article that the blood test from the doctor is more accurate than the DNA test on this.

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