>you can have it without the marker and be healthy with it That is literally true of every marker in existence. It's not the most specific marker, no, but if y

>you can have it without the marker and be healthy with it That is literally true of every marker in existence. It's not the most specific marker, no, but if you already have a strong prior for presence of autoimmune disease, then the presence or absence of that HLA subtype can point towards most likely root cause (autoimmune diseases are all incredibly similar in the early stages).