DISSEMINATED (systemic) lupus erythematosus is a relatively rare disorder. Little is known about its cause, but, because it has features in common with serum sickness, it has been postulated that the disease may be a manifestation of an antigen-antibody reaction.1 Other workers disagree with this concept.
Heidelberger2 has stated that complement acts as an "intensifier" of immune mechanisms. One of us (Mathieson) observed that serum from patients who had disseminated lupus erythematosus produced less hemolysis of sheep erythrocytes than did serum from normal persons. In nine patients who had lupus erythematosus, Sipos and Jáksó3 found normal values for complement in five, slight decrease in value in three, and pronounced decrease in one. In view of these observations, it was considered that an accurate determination of the amount of complement in serum by the quantitative methods developed by Mayer and associates4 and by Kent and co-workers