Human complement factor I(CFI) ELISA Kit

Trypsin-like serine protease that plays an essential role in regulating the immune response by controlling all complement pathways. Inhibits these pathways by cleaving three peptide bonds in the alpha-chain of C3b and two bonds in the alpha-chain of C4b thereby inactivating these proteins. Essential cofactors for these reactions include factor H and C4BP in the fluid phase and membrane cofactor protein/CD46 and CR1 on cell surfaces. The presence of these cofactors on healthy cells allows degradation of deposited C3b by CFI in order to prevent undesired complement activation, while in apoptotic cells or microbes, the absence of such cofactors leads to C3b-mediated complement activation and subsequent opsonization.

1. This study has revealed a significant genetic role for CFI-rs13104777 in acute anterior uveitis. This influence may be dependent on human leukocyte antigen (HLA)-B27 and disease laterality. PMID: 27380463
2. An extremely rare, heterozygous mutation in the gene encoding CFI likely affecting splicing was associated for the first time with atypical hemolytic uremic syndrome. PMID: 28455885
3. this study illustrates the importance of early versus late diagnosis of CFI deficiency PMID: 28942469
4. This finding although rare does suggest that screening for chromosomal rearrangements affecting CFI should be undertaken in all aHUS patients particularly if the factor I level is unexplainably low. PMID: 27268256
5. Factor I binds C3b-Factor H between Factor H domains 2 and 3 and a reoriented C3b C-terminal domain and docks onto the first scissile bond, while stabilizing its catalytic domain for proteolytic activity. PMID: 28671664
6. Taken together, our data argue that multiple rare and ultra-rare alleles in CFI contribute to AMD pathogenesis; they improve the precision of the assessment of the contribution of CFI to AMD PMID: 28282489
7. Case Report: thrombotic microangiopathy with mutations in complement factor I and thrombomodulin. PMID: 26613809
8. Our results indicate that CFI polymorphisms are not significantly associated with VKH syndrome. PMID: 26900322
9. Patients with advanced atrophic AMD carried these rare variants more frequently than patients with neovascular AMD (11 of 93 [11.8%] vs 40 of 835 [4.8%]; P = .04). PMID: 26767664
10. Low FI levels are strongly associated with rare CFI variants and age-related macular degeneration. PMID: 25788521
11. A missense variant (p.V412M) in CFI was discovered in two Tunisian Jewish families with early-onset age-related macular degeneration. PMID: 25986072
12. Regulatory components of the alternative complement pathway in endothelial cell cytoplasm, factor H and factor I, are not packaged in Weibel-Palade bodies. PMID: 25803806
13. In this study, the odds of AMD were highest in those with deficient vitamin D status and 2 risk alleles for the CFH and CFI genotypes, suggesting a synergistic effect between vitamin D status and complement cascade protein function. PMID: 26312598
14. iC3b level, a proteolytically inactive form of C3b, was lower in HCV infected patient sera, reflecting impairment of both C3 convertase and Factor I activity. PMID: 24983375
15. association between rs10033900 and age-related macular degeneration risk in Han Chinese population PMID: 24642830
16. The mutations in the regulators CFH, CFI and MCP involve loss-of-function, whereas those for C3 involve gain-of-function. PMID: 25188723
17. The CFI p.Gly119Arg mutation was identified in 7/521 age-related macular degeneration cases compared to 1/627 age-matched controls; this mutation confers a high risk of disease. PMID: 25352734
18. CFI genetic variants played an important role in the development of NSCLC in Chinese population. PMID: 25394898
19. High expression of complement factor I is associated with recurrence in breast cancer. PMID: 25618258
20. results provide evidence for the role of CFI in the progression of cSCC and identify it as a potential therapeutic target in this nonmelanoma skin cancer PMID: 25184960
21. This study has revealed a significant association between acute anterior uveitis (AAU) and CFI-rs7356506, suggesting that CFI is involved in the pathogenesis of AAU PMID: 25075123
22. Neither of the two SNPs most studied (rs10033900 or rs2285714) in the CFI gene was a risk factor for developing neovascular age-related macular degeneration or polypoidal choroidal vasculopathy in a Chinese population. PMID: 24732209
23. Recurrent aseptic meningo-encephalitis is a rare clinical presentation of complete FI deficiency. PMID: 24142231
24. An STR polymorphism in intron 7 of human CFI gene on chromosome 4q in 11 Asian populations indicated that Group H alleles in exon 11 of the CFI gene were almost entirely confined to East Asian populations, making it useful in forensic anthropology. PMID: 23688582
25. We found that 7.8% of advanced age-related macular degeneration cases compared to 2.3% of controls are carriers of rare missense CFI variants. PMID: 24036952
26. Case Report: patient with atypical haemolytic uremic syndrome with combined membrane cofactor protein CD46 and complement factor I mutations undergoing successful kidney transplantation. PMID: 23519521
27. Mutations in complement factor I protein is associated with end-stage renal disease in a patient with hemolytic uremic syndrome caused by infections by Escherichia coli strains producing Shiga-like toxins. PMID: 23731345
28. these findings demonstrate that rare, highly penetrant mutations in CFI contribute to the genetic burden of age-related macular degeneration. PMID: 23685748
29. rs1136287 in CFI is less likely to be associated in in extremely myopic Japanese individuals. PMID: 23722394
30. The alternative pathway of complement may play a role in the pathogenesis of HELLP syndrome. PMID: 22594569
31. Acute hemorrhagic leukoencephalitis (AHLE) is an unreported, rare phenotype for partial complement factor I deficiency. PMID: 22926405
32. we report four novel mutations and the first large gene deletion in the CFI locus. PMID: 22710145
33. One SNP (rs10033900) in the CFI gene, which encodes a protein involved in the inflammatory pathway, was significantly associated with myopic choroidal neovascularization in multivariate analysis after correction for multiple testing. PMID: 22678500
34. Since FI requires cofactors for its activity we also investigated the binding of purified cofactors C4BP and FH and found acquisition of both proteins, which retained their activity in FI mediated degradation of C3b and C4b. PMID: 22514678
35. factor I were significantly diminished early after trauma. PMID: 22258234
36. all analyzed cofactors form similar trimolecular complexes with FI and C3b/C4b, and the accessibility of FIMAC and SP domains is crucial for the function of FI PMID: 22393059
37. Results question whether complement factor I autoantibodies per se predispose to atypical hemolytic uremic syndrome. PMID: 22223611
38. Forster resonance energy transfer was used to investigate the 10 muM K(D) (210 kD) complex between the N-terminal region of the soluble complement regulator, factor H (FH1-4), and the key activation-specific complement fragment, C3b. PMID: 21936007
39. Data show that FI is in a proteolytically inactive form, demonstrating that it circulates in a zymogen-like state. PMID: 21768352
40. Study describes the molecular and functional consequences of two novel mutations of FI. PMID: 21316765
41. Study identified novel mutations in CFH, CFHR5, CFI, CFB and C3 in American patients with atypical hemolytic uremic syndrome. PMID: 20513133
42. Role of a common variant near the complement factor I gene in susceptibility to age-related macular degeneration. PMID: 20087399
43. In a large cohort of 202 patients with aHUS, we identified 23 patients carrying exonic mutations in CFI PMID: 20016463
44. the FIMAC domain appears to harbor the main binding sites important for the ability of FI to degrade C4b and C3b PMID: 20044478
45. mutations in complement factor I affect both secretion and function of factor I, which leads to impaired regulation of the complement system in atypical hemolytic uremic syndrome. PMID: 19877009
46. the last 45 amino acid of the heavy chain, including a disulfide bridge area, did not participate in the serine protease function of factor I PMID: 14967308
47. Human complement factor I does not require cofactors for cleavage of synthetic substrates. PMID: 15210795
48. fI and the serine protease domain were found to have similar amidolytic activities but strikingly different proteolytic activities on C3(NH(3)). PMID: 15835912
49. Mutations in the complement regulators factor H, membrane cofactor protein (MCP), and factor I are associated with atypical hemolytic uremic syndrome. PMID: 16386793
50. factor I in concert with CR1 on E and factor H in serum due to their cofactor activity are likely to be important contributors PMID: 16920989

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Hemolytic uremic syndrome atypical 3 (AHUS3); Complement factor I deficiency (CFI deficiency); Macular degeneration, age-related, 13 (ARMD13)

Secreted, extracellular space. Secreted.

Peptidase S1 family

Expressed in the liver by hepatocytes. Also present in other cells such as monocytes, fibroblasts or keratinocytes.

HGNC: 5394

OMIM: 217030

KEGG: hsa:3426

STRING: 9606.ENSP00000378130

UniGene: Hs.312485