TRAF1 and rheumatoid arthritis: TNF receptor-associated factor-1 (TRAF1) and Complement 5 (C5) (TRAF1-C5) lie adjacent to one another on 9q33-34 chromosome and confer susceptibility to diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) [19–22].