HLA-DRB1 and systemic lupus erythematosus: Summary of the association of HLA-DRB1*04 allele with cytokines and free radicals (IFN-γ, GM-CSF, IL-5, IL-17F, IL-18, IL-21, VEGF, LPO, and CAT) in Malay SLE patients and the involvement of these cytokines and free radicals in the pathogenesis of SLE and LN based on the findings adapted from different previously published studies.