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The Complement System, An Innate Immunity Station

The Complement System occupies a unique position among early cellular sensors, acting directly on the surface of triggering cells or substances to coordinate downstream cellular humoral immune responses. This makes this system a critical part of the immune cascade, contributing to both innate immune responses, including:

Local inflammation for removal and killing of pathogens

Signaling and influencing of T and B-cell biology

As a global regulator of immunity and tissue homeostasis, the Complement System has become an interesting, yet complex pharmacological target, contributing a network that contributes to pathogenesis in various inflammatory and neurodegenerative diseases, as well as, cancers.

Overall, the Complement-targeted therapies has been a very active field in recent years. Potent complement inhibitors are now available and increasingly used in approved and off-label indications that demonstrate the therapeutic potential of complement control.

Complement activation is implicated in numerous diseases

https://doi.org/10.1016/j.molimm.2019.07.030

Anti-complement drugs currently in clinical development

https://doi.org/10.1016/j.molimm.2019.07.030

A better understanding of the complement's structure, function, and biological role will support our complement-based understanding to contribute to treating inflammation, neurodegenerative diseases, and cancers. Complement-targeted drugs that intervene at the signaling cascade level can help to better tailor therapeutic strategies and allow such strategies to be applied to a wider range of indications. To assist with research h into the Complement system, ACROBiosystems has developed a series of recombinant complement proteins expressed by HEK293 Cells, including C2, C3, C5, C5a and complement factor D (CFD).

Product Features

Comprehensive catalog of Complement products are available

High purity and structural homogeneity verified by SDS-PAGE and SEC-MALS

Native conformation, various species, free protocols available

High biological activity verified by ELISA and cell-based assay

Product List

Complement C5

Complement C5a

Complement C3

Complement C3a

Complement C2

Complement C1S

Complement Factor B

Complement Factor D

Cat. No.	Molecule	Product Description	Species	Order Now
CO5-H82E9	Complement C5 Complement C5	Biotinylated Human Complement C5 Protein, His,Avitag™ (MALS verified)	Human	Order
CO5-H52Hx	Complement C5 Complement C5	Human Complement C5 (R885H) Protein, His Tag	Human	Order
CO5-H52Ha	Complement C5 Complement C5	Human Complement C5 Protein, His Tag, low endotoxin (MALS verified)	Human	Order
CO5-H52H7	Complement C5 Complement C5	Human Complement C5 (w917s) Protein, His Tag (MALS verified)	Human	Order
CO5-H5253	Complement C5 Complement C5	Human Complement C5 Protein, Fc Tag	Human	Order
CO5-M52H4	Complement C5 Complement C5	Mouse Complement C5 Protein, His Tag	Mouse	Order
CO5-C82E3	Complement C5 Complement C5	Biotinylated Cynomolgus Complement C5 Protein, His,Avitag™ (MALS verified)	Cynomolgus	Order
CO5-C52Hx	Complement C5 Complement C5	Cynomolgus Complement C5 Protein, His Tag (MALS verified)	Cynomolgus	Order
CO5-R82E3	Complement C5 Complement C5	Biotinylated Rat Complement C5 Protein, His,Avitag™	Rat	Order
CO5-R52H5	Complement C5 Complement C5	Rat Complement C5 Protein, His Tag	Rat	Order
CO5-R52H4	Complement C5 Complement C5	Rabbit Complement C5 Protein, His Tag	Rabbit	Order

Cat. No.	Molecule	Product Description	Species	Order Now
C5A-H525a	Complement C5a Complement C5a	Human Complement C5a Protein, Fc Tag (MALS verified)	Human	Order
C5A-H51H9	Complement C5a Complement C5a	Human Complement C5a Protein, His Tag	Human	Order
C5A-H5116	Complement C5a Complement C5a	Human Complement C5a Protein, Tag Free	Human	Order
C5A-M51H4	Complement C5a Complement C5a	Mouse Complement C5a Protein, His Tag	Mouse	Order
C5A-C51H9	Complement C5a Complement C5a	Cynomolgus Complement C5a Protein, His Tag	Cynomolgus	Order
C5A-C5118	Complement C5a Complement C5a	Cynomolgus Complement C5a Protein, Tag Free	Cynomolgus	Order

Cat. No.	Molecule	Product Description	Species	Order Now
CO3-H82E8	Complement C3 Complement C3	Biotinylated Human Complement C3 Protein, His,Avitag™ (MALS verified)	Human	Order
CO3-H52H3	Complement C3 Complement C3	Human Complement C3 Protein, His Tag, low endotoxin (MALS verified)	Human	Order
CO3-H5253	Complement C3 Complement C3	Human Complement component 3 Protein, Fc Tag (MALS verified)	Human	Order
CO3-M52H4	Complement C3 Complement C3	Mouse Complement C3 Protein, His Tag (MALS verified)	Mouse	Order
CO3-C52H5	Complement C3 Complement C3	Cynomolgus Complement C3 Protein, His Tag (MALS verified)	Cynomolgus	Order

Cat. No.	Molecule	Product Description	Species	Order Now
COA-H82Q3	Complement C3a Complement C3a	Biotinylated Human Complement C3a Protein, His,Avitag™	Human	Order
COA-H5143	Complement C3a Complement C3a	Human Complement C3a Protein, His Tag	Human	Order
COA-M5243	Complement C3a Complement C3a	Mouse Complement C3a Protein, His Tag (HPLC verified)	Mouse	Order

Cat. No.	Molecule	Product Description	Species	Order Now
CO2-H52H7	Complement C2 Complement C2	Human Complement C2 Protein, His Tag (MALS verified) (active enzyme)	Human	Order
CO2-M52H3	Complement C2 Complement C2	Mouse Complement C2 Protein, His Tag, low endotoxin (MALS verified)	Mouse	Order
CO2-C82E7	Complement C2 Complement C2	Biotinylated Cynomolgus Complement C2 Protein, His,Avitag™ (active enzyme, MALS verified)	Cynomolgus	Order
CO2-C52H8	Complement C2 Complement C2	Cynomolgus Complement C2 Protein, His Tag (active enzyme)	Cynomolgus	Order
CO2-D82E4	Complement C2 Complement C2	Biotinylated Canine Complement C2 Protein, His,Avitag™ (active enzyme)	Canine	Order
CO2-C52H3	Complement C2 Complement C2	Canine Complement C2 Protein, His Tag (MALS verified)	Canine	Order
CO2-R82E6	Complement C2 Complement C2	Biotinylated Rat Complement C2 Protein, His,Avitag™ (active enzyme)	Rat	Order
CO2-R82E3	Complement C2 Complement C2	Biotinylated Rabbit Complement C2 Protein, His,Avitag™ (active enzyme)	Rabbit	Order
CO2-D82E5	Complement C2 Complement C2	Biotinylated Porcine Complement C2 Protein, His,Avitag™ (active enzyme)	Porcine	Order

Cat. No.	Molecule	Product Description	Species	Order Now
COS-H52H3	Complement C1s Complement C1s	Human Complement C1s Protein, His Tag, low endotoxin (MALS verified)	Human	Order
COS-C52H3	Complement C1s Complement C1s	Cynomolgus Complement C1s Protein, His Tag (MALS verified)	Cynomolgus	Order

Cat. No.	Molecule	Product Description	Species	Order Now
CFB-H82E4	Complement Factor B Complement Factor B	Biotinylated Human Complement Factor B Protein, His,Avitag™ (MALS & SPR verified)	Human	Order
CFB-H52H3	Complement Factor B Complement Factor B	Human Complement Factor B Protein, His Tag (MALS & SPR verified)	Human	Order
CFB-C82Q3	Complement Factor B Complement Factor B	Biotinylated Canine Complement Factor B Protein, His,Avitag™	Canine	Order
CFB-C52Q3	Complement Factor B Complement Factor B	Unconjugated Canine Complement Factor B Protein, His,Avitag™	Canine	Order
CFB-R82Q3	Complement Factor B Complement Factor B	Biotinylated Rat Complement Factor B Protein, His,Avitag™	Rat	Order
CFB-R52Q3	Complement Factor B Complement Factor B	Unconjugated Rat Complement Factor B Protein, His,Avitag™	Rat	Order

Cat. No.	Molecule	Product Description	Species	Order Now
CFD-H52H8	Complement Factor D Complement Factor D	Human Complement Factor D / CFD Protein, His Tag (active enzyme)	Human	Order
CFD-H5256	Complement Factor D Complement Factor D	Human Complement Factor D / CFD Protein, Fc Tag	Human	Order
CFD-R52H3	Complement Factor D Complement Factor D	Rhesus macaque / Cynomolgus Complement Factor D / CFD Protein, His Tag (active enzyme)	Cynomolgus / Rhesus macaque	Order

Verification Data

High purity and structural homogeneity verified by SDS-PAGE and SEC-MALS

The purity of Human Complement C5a, Fc Tag (Cat. No. C5A-H525a) is more than 90% and the molecular weight of this protein is around 80-90 kDa verified by SEC-MALS.

The purity of Cynomolgus Complement C3, His Tag (Cat. No. CO3-C52H5) is more than 95% and the molecular weight of this protein is around 168-205 kDa verified by SEC-MALS.

High bioactivity verified by antibody binding

Immobilized Human Complement C5, His Tag (Cat. No. CO5-H52Ha) at 2 μg/mL (100 μL/well) can bind Eculizumab Biosimilar with a linear range of 0.1-4 ng/mL (Routinely tested).

Request Protocol

Immobilized Human Complement C5a, His Tag (Cat. No. C5A-H51H9) at 5 μg/mL (100 μL/well) can bind Monoclonal Anti-Human C5a Human Antibody, Human IgG1 with a linear range of 0.1-4 ng/ml (QC tested).

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High bioactivity verified by cell-based assay

Human Complement C5a, Tag Free (Cat. No. C5A-H5116) induce N-acetyl-β-D-glucosaminidase release from differentiated U937 cells. The ED50 for this effect is 0.215-0.323 μg/mL (Routinely tested).

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Reference

1. King B C, Blom A M. Intracellular complement: Evidence, definitions, controversies, and solutions[J]. Immunological Reviews, 2023, 313(1): 104-119.
2. Zelek W M, Xie L, Morgan B P, et al. Compendium of current complement therapeutics[J]. Molecular immunology, 2019, 114: 341-352.
3. Lubbers R, Van Essen M F, Van Kooten C, et al. Production of complement components by cells of the immune system[J]. Clinical & Experimental Immunology, 2017, 188(2): 183-194.
4. Ricklin D, Lambris J D. New milestones ahead in complement-targeted therapy[C]//Seminars in immunology. Academic Press, 2016, 28(3): 208-222.

FAQ

Which complement proteins should I select for studying different activation pathways?

C1s and C2 are relevant to the classical pathway, while Complement Factor B and Factor D are key components of the alternative pathway. C3 is the central convergence point, whereas C5 and C5a participate in terminal pathway activation and inflammatory signaling. Target selection should reflect the pathway stage being investigated.

What are the experimental differences among C3, C3a, C5, and C5a?

C3 and C5 are precursor proteins used in antibody-binding, cleavage-mechanism, and complement-inhibitor studies. C3a and C5a are cleavage-derived inflammatory mediators suitable for receptor-binding, inflammatory-signaling, and cell-based assays. C5a is particularly potent in chemotaxis and immune-cell activation.

Which complement protein format should I choose for ELISA, SPR, or cell-based assays?

His-tagged proteins support routine capture and binding assays. Biotinylated proteins containing an Avitag™ enable controlled immobilization for SPR, BLI, and ELISA. Tag-free proteins are preferred for cell-based assays focused on native activity, while Fc-fused proteins can provide added stability for selected assay formats.

Why should both binding and cell-based activity be evaluated for complement proteins?

Binding assays confirm interactions with antibodies or receptors, while cell-based assays determine whether the protein produces the expected biological response. For example, ACRO Human C5 binds Eculizumab Biosimilar, and tag-free Human C5a induces N-acetyl-β-D-glucosaminidase release from differentiated U937 cells.

How should I choose among human, mouse, and cynomolgus complement proteins?

Human proteins are suitable for immunization, therapeutic antibody screening, and human-target studies. Mouse proteins support studies linked to mouse disease models, while cynomolgus proteins can be used for preclinical cross-species binding evaluation. Comparing homologous proteins across species helps assess candidate cross-reactivity during drug development.

Introduction
Product Features
Product List
Verification Data
Reference
FAQ