Complement and systemic lupus erythematosus

Complement is implicated in the pathogenesis of systemic lupus erythematosus (SLE) in several ways and may act as both friend and foe. Homozygous deficiency of any of the proteins of the classical pathway is causally associated with susceptibility to the development of SLE, especially deficiency of the earliest proteins of the activation pathway. However, complement is also implicated in the effector inflammatory phase of the autoimmune response that characterizes the disease. Complement proteins are deposited in inflamed tissues and, in experimental models, inhibition of C5 ameliorates disease in a murine model. As a further twist to the associations between the complement system and SLE, autoantibodies to some complement proteins, especially to C1q, develop as part of the autoantibody response. The presence of anti-C1q autoantibodies is associated with severe illness, including glomerulonephritis. In this chapter the role of the complement system in SLE is reviewed and hypotheses are advanced to explain the complex relationships between complement and lupus.     

Congenital heart block and maternal systemic lupus erythematosus.

The association between infants with congenital heart block (CHB) and the presence or later development of maternal systemic lupus erythematosus or other connective-tissue disease (CTD) was reviewed in 67 cases. In 24 cases CHB was diagnosed at or before birth. Of nine necropsies on affected infants, seven showed endomyocardial fibrosis. The results suggest that one in three mothers who deliver babies with CHB have or will develop CTD. The association is probably explained by placental transfer of a maternal antibody. Awareness of the association may lead to prevention of the birth of children with CHB and better neonatal care of affected children.