Different HLA's have a tendency to make antibodies that match certain things. For example, rheumatoid arthritis is strongly associated with HLA-DR4 and SLE and MS have strong associations with HLA-DR3. This is true of autoinflammatory (non antibody mediated) diseases as well, and all the serognegative spondyloarthropathies (ankylosing spondylitis, reactive arthritis, psoriatic arthritis, etc.) are associated with HLA-B27. Psoriasis is associated with HLA-Cw6. The list goes on - name an autoimmune or autoinflammatory condition and it will have an HLA association. Without the right HLA's, your body won't make antibodies to certain self antigens (or will be much less likely to).
Is psoriasis considered autoimmune ?