CAT and systemic lupus erythematosus: We have performed a literature search and provide a brief summary on the cytokines and free radicals (IFN-γ, GM-CSF, IL-5, IL-17F, IL-18, IL-21, VEGF, LPO and CAT) that are significantly correlated with HLA-DRB1*04 allele in Malay SLE patients together with the evidence gathered from a number of previously published studies that depicted the involvement of these cytokines and free radicals in SLE and LN pathogenesis (Table 6).