title: Influence of factor D concentrations on fluid phase C3 activation, lysis of rabbit erythrocytes and solubilization of immune complexes.
abstract: Factor D depleted serum did not support hemolysis of rabbit erythrocytes and solubilization of performed immune complexes. Fluid phase C3 cleavage increased in a dose dependent manner when D protein was added to normal or to factor D depleted serum. During short incubation factor D concentrations were correlated with the capacity of serum to solubilize immune complexes and to lyse rabbit erythrocytes. With prolonged incubation, the hemolytic activity decreased in a factor D dose dependent manner. This was probably due to fluid phase breakdown of C3 and factor B in the presence of high factor D concentrations. Hypocomplementemic sera from patients with active systemic lupus erythematosus (SLE) did not support solubilization of bovine serum albumin (BSA) anti-BSA complexes when factor D was added in excess. Patients with polycystic kidney disease with reduced renal function and high factor D concentrations showed increased concentrations of circulating C3d/dg fragments. The possibility was considered that high factor D concentrations in uremia might promote fluid phase C3 degradation and thereby limit the in vivo efficiency of alternative pathway activation on target surfaces.
authors.affiliation: Department of Rheumatology, University Hospital of Lund, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Sturfelt
authors.forename: A G
authors.initials: AG
authors.lastname: Sjöholm
authors.forename: L
authors.initials: L
authors.lastname: Truedsson
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology*; D003167:Complement Activation / Q000187:drug effects; D003176:Complement C3 / Q000378:metabolism*; D003170:Complement Pathway, Alternative / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000276:immunology*; D006461:Hemolysis; D006801:Humans; D007122:Immunoelectrophoresis; D008180:Lupus Erythematosus, Systemic / Q000097:blood; D007690:Polycystic Kidney Diseases / Q000097:blood; D011817:Rabbits; D012697:Serine Endopeptidases / Q000494:pharmacology*
chemical_list: D000936:Antigen-Antibody Complex; D003176:Complement C3; D012697:Serine Endopeptidases