The complement system is an important part of the innate immunity and plays an essential role in the clearance of immunecomplexes and in the activation of the inflammatory process. Complement proteins provide rapid and efficient means to protect the host from invasive microorganisms. Associations between complement and diseases are observed in situations of complement deficiency, abnormalities in the regulation of the complement system and inflammation. Inappropriate or excessive activation of the complement can lead to harmful consequences due to severe inflammatory tissue destruction. Clinical and experimental evidences implicate the role of complement in the pathogenesis of numerous inflammatory diseases, which includes not only immune complex and autoimmune disorders, but also organ failure subsequent to sepsis, multiple trauma and burns. Genetic variability has been described for several components, control proteins and receptors of the complement system. Complement protein variability can currently be studied, both by phenotypic assessment of protein variants (phenotyping) and characterization of genomic DNA (genotyping). The genetic variability of complement proteins has provided some light on the pathogenesis of a large group of disorders. Association of different allotypic variants of the complement with immunemediated diseases such as systemic lupus erythematosus, rheumatoid arthritis, insulin-dependent diabetes mellitus, liver cirrhosis, autoimmune hepatitis, multiple sclerosis, celiac disease and IgA/IgG4 deficiency has been described by various authors. The aim of the present review is to provide recent knowledge of the genetics of complement, as well as of the participation of this system in the pathogenesis of different diseases.
complement system; allotypic variability; inflammation
