icon lock Secure Shipping Worldwide
cart Shopping Cart Cart (0)
Select Currency:




Native - Human Plasma
US $101.00
Vial Size
C1q component of the C1 complex of complement activation
Uniprot ID:  P0C862
mRNA RefSeq:  NM_001700.3
Protein RefSeq:  NP_001691
Autoantibodies directed to the C1q component of the C1 complex of complement activation were first described in the serum of patients with systemic lupus erythematosus (SLE). The presence of anti-C1q antibodies in SLE has been shown to correlate with a greater incidence of nephritis and the absence of anti-C1q is indicative that renal flares are unlikely to occur. Anti-C1q are also present in a range of other clinical conditions such as hypocomplementemic urticarial vasculitis syndrome (HUVS), autoimmune thyroid disease and mixed connective tissue disease, anti-glomerular basement membrane nephritis, hepatitis C and HIV infection. Anti-C1q antibodies also occur in the healthy population with an incidence of 2-8% that increases with age.

C1q associates with the proenzymes C1r and C1s to yield C1, the first component of the serum complement system. The collagen-like regions of C1q interact with the Ca2+-dependent C1r2C1s2 proenzyme complex, and efficient activation of C1 takes place on interaction of the globular heads of C1q with the Fc regions of IgG or IgM antibody present in immune complexes.

C1q is made up of six copies of 3 glycosylated polypeptides: the A-subunit (223 amino acids), the B-subunit (226 aminos acids) and the C-subunit (217 amino acids). Each subunit has a short cysteine-containing N-terminal region, followed by a collagen-like region of approximately 81 amino acids and then a globular domain of approximately 135 amino acids at the C-terminal. These C-terminal domains form a heterotrimeric globular head domain; A to B and C to C interchain disulphide bonds yield a six-subunit, two globular head structural unit. Three of these structural units associate to yield the complete hexameric C1q molecule that has a tulip-like structure.

Autoantibodies to C1q are believed to be directed against a neo-epitope on the collagen-like region that is only exposed upon binding of C1q to immunoassay plates. Anti-C1q binding to linear epitopes has also been reported, as well as to conformation-dependent epitopes and to cryptic epitopes that only become exposed after fragmentation of C1q. The use of purified C1q for the detection of autoantibodies in human serum has been described elsewhere.

PDF-logo-dl C1q datasheet
Systemic Lupus Erythematosus
Lupus Nephritis
Hypocomplementemic Urticarial Vasculitis Syndrome (HUVS)
Please log in to view certificates of analysis for this item
  • Agnello, V. et al. (1971) J. Exp. Med. 134, 228s
  • Uwatoko, S. et al. (1984) Clin. Immunol. Immunopathol. 30, 104
  • Antes, U. et al. (1988) Arthritis Rheum. 31, 457
  • Wener, M.H. et al. (1989) Arthritis Rheum. 32, 544
  • Siegert, C.E. et al. (1992) Clin. Exp. Rheumatol. 10, 19
  • Gunnarsson, I. et al. (1997) Br. J. Rheumatol. 36, 32
  • Siegert, C.E. et al. (1993) Ann. Rheum. Dis. 52, 851
  • Trendelenburg, M. et al. (1999) Arthritis Rheum. 42, 187
  • Fremeaux-Bacchi, V. et al. (2002) Nephrol. Dial. Transplant 17, 2041vMarto, N. et al. (2005) Ann. Rheum. Dis. 64, 444vWisnieski, J.J. & Jones, S.M. (1992) J. Immunol. 148, 1396
  • Potlukova, E. et al. (2008) Clin. Exp. Immunol. 153, 96
  • Coremans, I.E.M. at al. (1992) Clin. Exp. Immunol. 87, 256
  • Saadoun, D. et al. (2006) Clin. Exp. Immunol. 145, 308
  • Prohaszka, Z. et al. (1999) Clin. Immunol. 90, 247
  • Horvath, L. et al. (2001) Immunol. Lett. 75, 103
  • Kishore, U. & Reid, K.B.M. (2000) Immunopharmacol. 49, 159
  • Arlaud, G.J. et al. (2001) Immunol. Rev. 180, 136
  • Kishore, U. et al. (2004) Immunol. Lett. 95, 113
  • Gaboriaud, C. et al. (2003) J. Biol. Chem. 278, 46974
  • Sellar, G.C. et al. (1991) Biochem. J. 274, 481
  • Kishore, U. e& Reid, K.B.M. (1999) Immunopharmacol. 42, 15
  • Trendelenburg, M. (2005) Springer Semin. Immunopathol. 27, 276
  • Siegert, C.E. et al. (1999) Clin. Exp. Immunol. 116, 4
  • Vanhecke, D. et al. (2012) Arthritis Rheum. 64, 3706
  • Stoyanova, V. et al. (2012) Immunol. Lett. 148, 69
  • Kohro-Kawata, J. et al. (2002) J. Rheumatol. 29, 84
  • Mahler, M. et al. (2013) Front. Immunol. 4, 1

You might also be interested in ...

Annexin A3

Annexin A3

Native - Human Neutrophils
US $364.00
Vial Size
Beta-2-Glycoprotein 1

Beta-2-Glycoprotein 1

Native - Human Plasma
US $488.00
Vial Size


Native - Human Leukocytes
US $478.00
Vial Size


Native - Human Neutrophils
US $590.00
Vial Size
AROTEC Diagnostics
AROTEC have been producing and supplying premium reagents to the diagnostic industry since our incorporation in 1996
Read More
Contact Us


+64 4569 0361

207 Gracefield Road,
Lower Hutt,