Crohn's and several forms of arthritis are closely linked to the HLA-B27 gene. (And I should know, because I have the whole shebang :P)
There have been some (tenuous) hypotheses suggesting that certain types of otherwise-benign gut infections in HLA-B27+ people basically short-circuit your immune system and teach it to attack its own tissues. So if you're HLA-B27+ you're not guaranteed to have an autoimmune disease, but you're potentially one bad stomach bug away from developing one.
Which, to be fair, all of this is still highly speculative, and it seems like even the hypotheses treat the resulting arthritis/IBD as an immune condition rather than a bacterial condition—Remicade et al are our best bet either way. But I'd love to one day unravel how a single gene can singlehandedly mess up your spine and your gut and your eyes and your skin!
There have been some (tenuous) hypotheses suggesting that certain types of otherwise-benign gut infections in HLA-B27+ people basically short-circuit your immune system and teach it to attack its own tissues. So if you're HLA-B27+ you're not guaranteed to have an autoimmune disease, but you're potentially one bad stomach bug away from developing one.
Which, to be fair, all of this is still highly speculative, and it seems like even the hypotheses treat the resulting arthritis/IBD as an immune condition rather than a bacterial condition—Remicade et al are our best bet either way. But I'd love to one day unravel how a single gene can singlehandedly mess up your spine and your gut and your eyes and your skin!