Although the etiology of systemic lupus erythematosus is unknown, recent studies have shed light on the pathogenetic pathways that lead to tissue damage. The immune system in systemic lupus erythematosus is characterized by a complex interplay between overactive B cells, abnormally activated T cells, and antigen-presenting cells. This leads to the production of an array of inflammatory cytokines, diverse autoantibodies, and immune complexes that in turn activate effector cells and the complement system leading to the clinical manifestations of the disease.