Some polymorphisms are common risk factors for autoimmune disease development, e.g. TNF-308A variant of TNF gene at 6p21.3 for SLE, RA and primary SS and some are disease-specific, like CCR5 gene at 3p21.31 and IL1B at 2q13 for SLE.[43] Susceptibility to SLE also involves class II MHC gene polymorphism. Here, CCR5 is linked to systemic lupus erythematosus.