title: Cartilage oligomeric matrix protein-induced complement activation in systemic sclerosis.
abstract: BACKGROUND
  Complexes between cartilage oligomeric matrix protein (COMP) and the complement activation product C3b have been found in the circulation of patients with rheumatoid arthritis and systemic lupus erythematosus. In systemic sclerosis (SSc) COMP expression in the skin is upregulated both in lesional and non-lesional skin, which is also reflected in an increased amount of circulating COMP. We investigated the presence of COMP-C3b complexes in serum and skin biopsies of patients with SSc.
  
  
  METHODS
  The presence of COMP and COMP-C3b complexes in the serum of 80 patients with limited cutaneous SSc (lcSSc, n = 40) and diffuse cutaneous SSc (dcSSc, n = 40) and 97 healthy controls was measured by ELISA and correlated to different clinical parameters. Samples were collected both at baseline and after three to five years to assess longitudinal changes in COMP-C3b complex levels. Furthermore, skin biopsies from seven patients with dcSSc and three healthy controls were analyzed for expression of COMP and deposition of C3b and IgG.
  
  
  RESULTS
  Serum levels of COMP-C3b were found to be elevated in both dcSSc and lcSSc compared to healthy controls and decreased at the second measurement in patients on immunosuppressive therapy. No co-localization of COMP and C3b was found in the skin biopsies, indicating that the COMP-C3b complexes are formed upon release of COMP into the circulation.
  
  
  CONCLUSIONS
  COMP-C3b complexes are found in the serum of patients with SSc. The lack of co-localization between COMP and C3b in the skin suggests that COMP does not drive complement activation in the skin in SSc.
authors: Kaisa E
authors: KE
authors: Otteby
authors: Emelie
authors: E
authors: Holmquist
authors: Tore
authors: T
authors: Saxne
authors: Dick
authors: D
authors: Heinegård
authors: Roger
authors: R
authors: Hesselstrand
authors: Anna M
authors: AM
authors: Blom
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D064236:Cartilage Oligomeric Matrix Protein / Q000032:analysis / Q000097:blood*; D003167:Complement Activation / Q000502:physiology*; D003179:Complement C3b / Q000032:analysis / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D012595:Scleroderma, Systemic / Q000097:blood*; D012867:Skin / Q000378:metabolism; D055815:Young Adult
chemical_list: D064236:Cartilage Oligomeric Matrix Protein; D003179:Complement C3b; C577553:TSP5 protein, human