Tissue i n j u r y o c c u r r i n g i n p a t i e n t s w i t h SLE appears t o be mediated p r i m a r i l y by complement f i x i n g immune complexes comprised o f autoantibodies and autoantigens. Cytotoxic antibodies which d i r e c t l y i n t e r a c t w i t h i n s i t u membrane antigens, e.g. a n t i -r e d blood c e l l antibodies, p l a y a more l i m i t e d r o l e i n t h e pathogenesis o f t h i s disease. Other autoantibodies such as antibodies r e a c t i v e w i t h p l a t e l e t s have been associated w i t h thrombocytopenia a1 though immune complexes may i n t e r a c t w i t h Fc receptors causing aggregation o f p l ate1 e t s and thereby c o n t r i b u t e t o increased clearance and thrombocytopenia.
Antilymphocyte antibodies, a heterogeneous population o f molecules r e a c t i v e w i t h m u l t i p l e membrane determinants, have been associated w i t h lymphopenia, i m p l i c a t e d i n t h e process o f immunoregulation, and form c o l d p r e c i p i t a b l e immune complexes containing lymphocyte surface antigens. The importance o f c e l l u l a r immune mechanisms such as antibody depende n t c e l l c y t o t o x i c i t y , s e n s i t i z e d T c e l l s and n a t u r a l k i l l e r c e l l s remains t o be c l a r i f i e d .
Therefore, immune complexes p l a y a c e n t r a l r o l e i n t h e pathogenesis o f SLE, and a r e manifested as a chronic serum sickness disease w i t h i n t e r m i t t e n t exacerbations and remissions.
The major organ systems a f f e c t e d by immune complexes and/or autoantibodies a r e l i s t e d i n Table 1. Imwne complex d e p o s i t i o n has been c l o s e l y c o r r e l a t e d w i t h h i s t o l o g i c evidence o f inflammatory l e s i o n s and d y s f u n c t i o n o f renal glornerul i f renal tubules, blood vessels, synovial tissues, p l e u r a l and p e r i c a r d i a l membranes and a l v e o l a r septae o f t h e lung (1-6).
The pathogenesis o f c e n t r a l nervous system (CNS) disease, p a r t i c u l a r l y d i f f u s e b r a i n syndromes such as psychoses and convulsions has n o t been c l e a r l y characterized as r e l a t e d t o e i t h e r autoantibodies o r immune complexes. The immune complex deposits found i n t h e choroid plexus