Ficolins are a group of proteins containing both a collagen-like domain and a fibrinogen-like domain. Three forms of ficolins have been identified in humans: Ficolin-1 (M-ficolin), Ficolin-2 (L-ficolin),and Ficolin-3 (H-ficolin). Ficolin-2 is produced primarily by the liver. Whereas Ficolin-3 is produced by the liver and the lung and Ficolin-1 by monocytes, leukocytes and lung cells. Ficolin-2 recognizes distinct danger-associated molecular patterns (DAMPs) like GlcNAc-structures in Lipoteichoic Acid (LTA) and fungal 1,3-β-D-glucan. Ficolin-2 also recognizes N-acetylated compounds such as acetylcholine.
Furthermore, Ficolin-2 recognizes apoptotic cells and participates in the removal of host cells. Ficolin-2 circulates in complex with MASP-2 and can activate the lectin complement pathway. Ficolin-2 serum levels are reported with varying concentrations. Polymorphisms in the promoter of the FCN2 gene from which Ficolin-2 is derived are associated with variation in Ficolin-2 serum levels. These polymorphisms may influence the affinity of Ficolin-2 to GlcNAc-structures.
Ficolin-2 deficiencies have not been reported, but low Ficolin-2 serum levels have been associated with recurrent respiratory infections in children. Interestingly, Ficolin-2 has been implicated in the unique immune challenge during pregnancy. In maternal plasma of normal pregnancies, a 4- to 5-fold increase in Ficolin-2 was detected compared to healthy non-pregnant persons. However, significantly lower Ficolin-2 maternal plasma concentrations were associated with pre-eclamptic pregnancies. Therefore, assessment of Ficolin-2 is warranted to study its regulatory role in the innate immune system. Normal human plasma contains a Ficolin-2 concentration ranging from 1 to 14 µg/ml.
The human Ficolin-2 ELISA kit is to be used for the in vitro quantitative determination of human Ficolin-2 in serum, plasma and cell culture supernatant samples.
The human Ficolin-2 ELISA is a ready-to-use solid-phase enzyme-linked immunosorbent assay based on the sandwich principle with a working time of 3½ hours.
The efficient format of 2 plates with twelve disposable 8-well strips allows free choice of batch size for the assay.
Samples and standards are captured by a solid bound specific antibody.
Biotinylated tracer antibody will bind to captured Ficolin-2.
Streptavidin-peroxidase conjugate will bind to the biotinylated tracer antibody.
Streptavidin-peroxidase conjugate will react with the substrate, tetramethylbenzidine (TMB).
The enzyme reaction is stopped by the addition of oxalic acid.
The absorbance at 450 nm is measured with a spectrophotometer. A standard curve is obtained by plotting the absorbance (linear) versus the corresponding concentrations of the Ficolin-2 standards (log).
The human Ficolin-2 concentration of samples, which are run concurrently with the standards, can be determined from the standard curve.
The linearity of the assay was determined by serially diluting a sample containing 6903 ng/ml human Ficolin-2. The diluted samples were measured in the assay. The line obtained a slope of 1.11 and a correlation coefficient of 0.998.
Normal human blood samples (plasma), containing baseline levels of 500 ng/ml were spiked with recombinant Ficolin-2 in concentrations of 20 and 200 ng/ml. Samples with and without Ficolin-2 were incubated for 1 hour at 37 °C. Samples were measured using the ELISA. Recovery values for Ficolin-2 ranged between 100 % and 110%.