Abstract
Middle-aged female identical twins, one of whom had systemic lupus erythematosus (SLE), were evaluated for immunologic reactivity to previous antigenic challenges, including primary immunization with a foreign antigen, keyhole limpet hemocyanin (KLH). These two women had lived together for all of their 58 years and neither was receiving anti-inflammatory or immunosuppressive drugs at the time of these studies. Both twins demonstrated comparable 7S and 198 humoral antibody response to KLH, as well as similar viral antibody titers. However, the twin with SLE was anergic to common antigens, streptokinase-streptodornase, Trichophyton and Candida; furthermore delayed hypersensitivity to KLH did not develop after immunization. This observed discrepancy between humoral and cellular immunity in genetically similar subjects may be significant in the pathogenesis of SLE.