If you’re anything like me, the next couple sentences are likely to be the most boring you’ll be reading in a while. Stick with me, though, because it’s critical stuff. This alphanumerical string, HLA-B27, is the flag shared by 95% of ankylosing spondylitis sufferers. Yet, HLA-B27 is an uncommon allele, shared only by an estimated of 8% or less of the general population. This is a clear correlation between genetic makeup and the likelihood of an AS diagnosis. Yet, only 10% to 20% of HLA-B27 carriers appear to have symptoms of ankylosing spondylitis.
In simpler terms? HLA-B27 is something few people are born with. And an even smaller subset of that minority end up with ankylosing spondylitis. Yet almost all ankylosing spondylitis sufferers test positive for HLA-B27. That isn’t to say that you can’t test negative for HLA-B27 and still have ankylosing spondylitis. It just means that scenario is much less likely.
What is HLA-B27?
HLA-B27 stands for ‘Human Leukocyte Antigen, subtypes B2701 through B2759.’ It’s discovery is relatively new to the ankylosing spondylitis scene. While likely not the only genetic marker for the disease, it’s clear correlation with AS was first noticed in 1973. Since then, it’s become the most studied of the HLA-B group in your blood, though no one is yet certain how it influences arthritis.
Anyone who paid attention during health class in high school knows that we all have white blood cells and red blood cells. White blood cells function as agents of the immune system, testing cells for infection throughout the body. But, in the case of ankylosing spondylitis, the immune system gets confused. The white blood cells end up attacking healthy cells, causing all the other unpleasant symptoms of the disease. Human leukocyte antigens are the proteins located on the surface of these white blood cells. The B27 subtype of these proteins help these cells identify problems and infections within the body.
Where did it come from?
The current theory is that HLA alleles became incorporated into the homo sapien bloodstream when our ancestors mated with neanderthals. This was an important development for us as a species, granting us immunity from diseases that the neanderthal population had already adapted to outside of the African continent.
Most doctors won’t test you for HLA-B27 until there’s a convergence of ankylosing spondylitis symptoms. After all, just because your white blood cells happen to carry the subtype of the B27 proteins doesn’t mean you’re doomed to a future of autoimmune disease. This is why it’s important, early on, to talk to you doctor. You want to make sure to get tested for this specific genetic marker if you so much as think that you may be suffering the early symptoms of AS.
My personal, and incredibly unscientific, opinion is that being born with HLA-B27 is just the first step on the path to developing spondyloarthropy.
If I was a betting man, I’d put my money on the fact that future research into this aspect of ankylosing spondylitis will reveal potential triggers tied to diet, behavior and more.