Previous models used to explain the association between HLA DR4 and rheumatoid arthritis (RA) focused on the presentation of 'arthritogenic' peptides. These failed because of the diversity of HLA molecules that are associated with the disease. Patients with RA have accelerated erosion of telomeres in peripheral T cells. Recent research shows that this might be a function of HLA DR4 expression and is common to all blood cells. This offers a new perspective on the mechanism of HLA disease associations and also a link to T-cell homeostasis, which is known to be important in RA.