B2M and rheumatoid arthritis: Some investigators have found that the expression of beta 2 microglobulin elevated in some immune diseases, such as systemic lupus erythematosus (SLE) (11, 13), rheumatoid arthritis (RA) and Sjögren's syndrome (14–16), and anti-beta2 microglobulin was also detected in SLE patients (17–19).