The Quantikine Human soluble CD14 Immunoassay is a 4.5 hour solid phase ELISA designed to measure human soluble CD14 in cell culture supernates, serum, and plasma. It contains recombinant human CD14 expressed from CHO cells and antibodies raised against the recombinant factor. This immunoassay has been shown to accurately quantitate the recombinant factor. Results obtained measuring natural ...human sCD14 showed dose-response curves that were parallel to the standard curves obtained using the kit standards. These results indicate that this kit can be used to determine relative mass values for natural human sCD14.
Store the unopened product at 2 - 8 °C. Do not use past expiration date.
This product is produced by and ships from R&D Systems, Inc., a Bio-Techne brand.
Alternate Names for Human CD14 Quantikine ELISA Kit
monocyte differentiation antigen CD14
Myeloid cell-specific leucine-rich glycoprotein
CD14 is a glycoprotein that mediates the interaction of lipopolysaccharide (LPS, endotoxin)with cells, thereby signaling the presence of gram-negative bacteria (1-3). CD14 is eithersoluble (CD14) (4, 5) or membrane-bound (mCD14) by a glycosylphosphatidylinositol (GPI)anchor (6, 7). mCD14 is a 55 kDa glycoprotein (1), while CD14 varies from about 43 to 53 kDa,depending on the degree of glycosylation and whether it was synthesized without the anchoror was shed by phospholipase cleavage of the anchor or by proteolysis (12-14). There is noevidence for different mRNAs for m- and CD14. There is no apparent sequence homology withother proteins. The sequence of human CD14 is 63-73% identical to that of mouse, rat, or rabbitCD14 (15).
mCD14 is expressed primarily on myeloid cells, such as monocytes, macrophages andneutrophils (1-3), the cells most sensitive to LPS, and to a lesser extent on other cells, such as Bcells (8) and a circulating dendritic cell progenitor (9). CD14 appears to mediate LPS stimulationof cells that do not express mCD14 (10, 11), such as endothelial, epithelial and smooth-musclecells. CD14 is found in both serum and urine (5).
The binding of LPS to CD14 requires an acute phase protein, LPS-binding protein (LBP) (16).The relationship of mCD14, CD14, LPS and LBP is complicated. At low concentrations of LPS,LBP is essential for the binding of LPS to CD14, but at high concentrations, LBP may actuallyinhibit binding of LPS to CD14. In addition, CD14 may compete with mCD14 for LPS (17) andmay serve to help clear LPS (18). These four factors thus appear to participate in a complexfeedback mechanism of immune regulation involving both up-regulation and down-regulationof the inflammatory process triggered by LPS. It is loss of control of this mechanism thatappears to lead to septic shock. LPS-bound CD14 signals production of inflammatory cytokinesand other inflammatory proteins, but the mechanism of signal transduction is unclear. Sincea GPI anchor is not transmembrane, there presumably is another transmembrane protein oncells through which LPS-bound CD14 transmits a signal (19).
In addition to its well known role in gram-negative infections, CD14 likely serves otherfunctions as well. It recognizes soluble peptidylglycan from gram-positive cell walls (20), and ithas been reported to bind apoptotic cells and induce their phagocytosis (21).
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