Mouse CD14 Quantikine ELISA Kit Summary

Product Summary

The Quantikine Mouse CD14 Immunoassay is a 4.5 hour solid phase ELISA designed to measure mouse CD14 levels in cell culture supernates, serum, and plasma. It contains NS0-expressed recombinant mouse CD14 and antibodies raised against the recombinant factor. This immunoassay has been shown to quantitate the recombinant mouse CD14 accurately. Results obtained using natural mouse CD14 showed dose-response curves that were parallel to the standard curves obtained using the recombinant kit standards. These results indicate that this kit can be used to determine relative mass values for natural mouse CD14.

Preparation and Storage

Background: CD14

CD14 is an acute phase glycoprotein that binds lipopolysaccharide (LPS) endotoxins with cells, thereby signaling the presence of gram-negative bacteria (1-4). Its 11 leucine-rich repeats mediate the interaction with LPS. The 55 kDa form, mCD14, is anchored to the membrane via glycosylphosphatidylinositol (GPI) linkage (1, 2, 5-7). Human mCD14 shares 63-73% amino acid sequence identity with mouse, rat or rabbit CD14. Soluble forms of CD14, or sCD14, may be secreted prior to GPI linkage or shed by proteolysis or cleavage of the GPI linkage. This variation, plus variable glycosylation, creates forms that may range from 43 to 53 kDa (8-10). In humans, the N terminal 13 kDa, termed presepsin or sCD14-ST, is a small soluble subtype that is found in plasma during sepsis or local infection (11-13). Membrane CD14 is expressed primarily on the cells that are most sensitive to LPS, including monocytes, macrophages and neutrophils (1-3). Lower amounts are detected on other cells, such as B cells, epithelial cells, endothelial cells, and fibroblasts (1, 14-16). Soluble CD14 is found in serum, urine and other body fluids (5).  

CD14 cooperates with another acute phase protein, LBP (LPS-binding protein), which binds LPS and transfers it to CD14 (1-3, 17). LPS can be further transferred from CD14 to the TLR4/MD2 complex on the cell surface (1). LPS causes signaling via clustering of LPS-bound CD14/TLR4/ MD2 complexes within cholesterol-rich lipid rafts (1). These signals induce production of inflammatory cytokines and other inflammatory proteins (18, 19). When uncoordinated, the signals contribute to septic shock (1). CD14 potentiates TLR-mediated signals triggered by microbe-derived ligands other than LPS, including TLR2 activation by polymeric peptidoglycan, gram-positive bacterial lipoteichoic acid, or mycobacterial lipoarabinomannan (1, 20). It increases uptake and trafficking of the viral TLR3 ligand, poly(I:C) (1, 20). In the lungs, CD14 binds phosphoinositides and surfactant proteins, such as SP-A and SP-D, via interaction of lipids with the CD14 LPS binding site (21, 22). CD14 may also bind ICAM-3 on apoptotic leukocytes and induce phagocytosis (23).  

High concentrations of sCD14 may inhibit LPS-mediated responses by competing for binding to mCD14 (24). In the presence of LBP, however, sCD14 can also potentiate LPS responses or help cells to clear circulating LPS, whether or not the cells express mCD14 (16-19). At low concentrations of LPS, both sCD14 and mCD14 can mediate endothelial cell responses such as upregulation of E-selectin, while response to intermediate concentrations of LPS requires mCD14 (16). Circulating sCD14, especially presepsin, is increased in sepsis and may correlate with severity (11, 12). sCD14 may be increased as compared to normal circulating sCD14 in some autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis, but decreased in others, such as Crohn's disease (25-27). sCD14 can also modulate inflammation-driven insulin resistance (28).

Assay Procedure

Refer to the product datasheet for the complete assay procedure.

Bring all reagents and samples to room temperature before use. It is recommended that all samples, standards, and controls be assayed in duplicate.

1、Prepare all reagents, standard dilutions, and samples as directed in the product insert.

2、Remove excess microplate strips from the plate frame, return them to the foil pouch containing the desiccant pack, and reseal.

3、Add 50 μL of Assay Diluent to each well.

4、Add 50 μL of Standard, control, or sample to each well. Cover with a plate sealer, and incubate at room temperature for 2 hours.

5、Aspirate each well and wash, repeating the process 4 times for a total of 5 washes.

6、Add 100 μL of Conjugate to each well. Cover with a new plate sealer, and incubate at room temperature for 2 hours.

7、Aspirate and wash 5 times.

8、Add 100 μL Substrate Solution to each well.

9、Add 100 μL of Stop Solution to each well. Read at 450 nm within 30 minutes. Set wavelength correction to 540 nm or 570 nm.