Chapter 19 - Immune Complexes in Systemic Lupus Erythematosus

Abstract

Systemic lupus erythematosus (SLE) is the prototype of autoimmune diseases that are principally mediated by immune complexes. This chapter deals with the immune complexes in SLE. Immune complexes are composed of antigens and antibodies. The chemical features and physical characteristics of antigens can be quite variable, ranging from simple molecules to complex macromolecules or tissue components. Antibodies in immune complexes may belong to any of the classes of immunoglobulins and endow the complexes with biologic properties unique to the particular class of immunoglobulin. In addition, the nature of the bond between the antigen and antibody influences the biologic properties of the resultant immune complexes. Among the many properties of immune complexes, activation of the complement systems, interaction with cell receptors, and deposition in tissues are most relevant to SLE pathogenesis. Interactions with cells are mediated largely through Fc and complement receptors present on a variety of cell types. The degree of these biologic activities depends in part on the class or subclass of antibodies in the immune complexes and on the degree of lattice formation in the complexes. Immune complexes, especially those containing DNA or other nucleic acid antigens, play a central role as initiators and amplifiers of the abnormal inflammatory and immune response characteristic of SLE. Immune complexes play a pivotal role in the pathogenesis of lupus nephritis as well as other manifestations of SLE, and understanding the pathophysiology could provide a useful basis for further therapies.