Inhibition of complement activation in aged individuals due to increased plasma fibronectin concentration.
The influence of fibronectin levels on complement activation by immune complexes and non-immune activators in elderly humans was investigated. The present study demonstrates for the first time a shift in complement activation from the classical to the alternative pathway, if the fibronectin concentration rises above a certain level (near 1 mg/ml). Plasma of elderly individuals often contains large amounts of fibronectin, the reason for which is unknown. While C1 consumption is inhibited under these conditions, C3 depletion remains largely unaffected. This could be due to a compensatory triggering of the alternative reaction sequence caused by fibronectin deposition at and blockade of C1-activating sites. Probable physiologic implications of this changed complement activation pattern are discussed.
Menzel
J E
JE
Ludwig Boltzmann Institut für Altersforschung, Universität Wien, Austria.
Dunky
A
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003167:Complement Activation; D003172:Complement C1 / Q000276:immunology; D003176:Complement C3 / Q000276:immunology; D003181:Complement C4 / Q000276:immunology; D003170:Complement Pathway, Alternative; D003171:Complement Pathway, Classical; D005353:Fibronectins / Q000097:blood*; D006801:Humans
D003172:Complement C1; D003176:Complement C3; D003181:Complement C4; D005353:Fibronectins