Factor B (complement fragment Bb)ELISA Kit

Name: Factor B (complement fragment Bb)ELISA Kit
SKU: DEIASL036
Rating: 5 (1 reviews)

Regulatory status: For research use only, not for use in diagnostic procedures.

COA

SDS

Datasheet

Summary

Sample

Serum, EDTA plasma

Species Reactivity

Human

Detection Method

Sandwich-ELISA

Intended Use

DEIASL036 detects complement factor B activation fragment.
This enzyme-linked immunosorbent assay (ELISA) kit is specifically designed for the quantitative detection of complement fragment Bb—a key activation byproduct of Factor B within the alternative complement pathway—in human serum and plasma matrices. Quantifying Bb levels serves as a reliable indicator of alternative pathway activation. Evaluating this activation is diagnostically valuable for a range of renal conditions (such as lupus nephritis and chronic glomerulonephritis) and dermatological disorders (including pemphigus vulgaris and dermatitis herpetiformis). Furthermore, elevated alternative pathway activity is frequently documented in pathologies like sickle cell anemia, rheumatoid arthritis, and infections caused by gram-negative bacteria.

Contents of Kit

No.	Components	Size	Storage Conditions
1	Coated Strips	12×8 wells	2-8°C
2	Standards (lyophilized)	1mL × 5	2-8°C
3	Low Controls (lyophilized)	1mL × 1	2-8°C
4	High Controls (lyophilized)	1mL × 1	2-8°C
5	Stop Solution	12mL × 1	2-8°C
6	20× Wash Buffer	50mL × 1	2-8°C
7	Complement Specimen Diluent	50mL × 1	2-8°C
8	TMB Substrate	12mL × 1	2-8°C
9	HRP Conjugate	7mL × 1	2-8°C
10	Hydrating Reagent	25mL × 1	2-8°C

Storage

Store the unopened kit at 2°C to 8°C. After the kit is opened, the 20× Wash Solution Concentrate and Hydrating Reagent may be stored at 2°C to 25°C.
All reagents must be brought to room temperature (15°C to 25°C) before use. Place all unused microassay strips into the storage bag, reseal the bag, and store at 2°C to 8°C.

Precision

Intra-assay CV and Inter-assay CV was determined by assaying 20 replicates of 2 plasma samples and 2 serum samples in 3 different runs.

Sensitivity

LOD: The limit of detection (LOD) is 0.018 μg/mL, determined by the upper 3SD limit in a zero standard study.
LLOQ: The lower limit of quantitation (LLOQ) is 0.033 μg/mL, the lowest concentration on the standard curve that met NCCLS criteria for accuracy and precision.
ULOQ: The upper limit of quantitation (ULOQ) is 0.836 μg/mL, the highest concentration that met NCCLS criteria for accuracy and precision.

General Description

Operating independently of specific antibodies, the alternative complement pathway is a crucial component of the innate immune defense against microbial pathogens. Activation can be initiated by various stimuli, including gram-negative bacterial lipopolysaccharides (LPS), microbial lipids and polysaccharides, as well as distinct surface markers present on cancer cells, parasites, and virus-infected mammalian cells. Notably, aberrant activation of this pathway frequently exacerbates tissue injury in autoimmune disorders.
A pivotal event in this pathway is the transformation of the 93 kDa zymogen, Factor B, into an active proteolytic enzyme via a two-stage cascade. Initially, Factor B associates with either C3b or C3(H₂O) to form a magnesium-dependent complex. While the C3(H₂O),B complex forms exclusively in the fluid phase, the C3b,B complex can assemble on target cell surfaces or in solution. Subsequently, the alternative pathway enzyme, Factor D, cleaves the complex-bound Factor B into two fragments: Ba (33 kDa) and Bb (60 kDa). This cleavage generates the C3b,Bb bimolecular complex, which functions as the alternative pathway C3 convertase. The catalytically active Bb subunit then cleaves C3 into C3a and C3b. The accumulation of C3b allows for the formation of the C3b,Bb,C3b trimolecular complex—the C5 convertase—responsible for processing C5 into C5a and C5b.
The stability of these C3 and C5 convertases is enhanced by Factor P (Properdin), a naturally occurring plasma protein, or by C3 nephritic factor, an autoantibody found in patients with severe alternative pathway overactivation. Conversely, these convertases are negatively regulated and inactivated through spontaneous dissociation or via interaction with regulatory proteins like Complement Receptor 1 (CR1) and Factor H. Even after dissociation, the free Bb fragment maintains certain biological functions, such as plasminogen activation, macrophage spreading induction, and functional hemolytic activity.
Although typically characterized as antibody-independent, the alternative pathway can be secondarily amplified by classical pathway activation. For instance, immune complexes in autoimmune diseases trigger the classical cascade, generating C3b fragments. These fragments subsequently bind Factor B, initiating its cleavage and amplifying complement activation, which can significantly worsen localized tissue destruction.
By evaluating Factor B cleavage products in biological samples, researchers can gauge the magnitude of alternative pathway engagement at the time of sample collection. This ELISA kit offers a quantitative, highly specific, rapid, and non-isotopic method for measuring Factor B activation. It serves as an excellent analytical tool for investigating alternative complement dynamics across clinical and research environments, as well as for monitoring in vitro Bb generation.

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