CD14

CD14

Diagram of Toll-like receptor pathways, including CD14 involvement.

CD14 is a glycoprotein that plays a crucial role in the immune system as a co-receptor for the detection of bacterial lipopolysaccharides (LPS). It is primarily expressed on the surface of macrophages and neutrophils, and it is involved in the activation of the innate immune response.

Structure

CD14 is a 55-kDa glycoprotein that exists in two forms: a membrane-bound form (mCD14) and a soluble form (sCD14). The membrane-bound form is anchored to the cell surface via a glycosylphosphatidylinositol (GPI) anchor, while the soluble form is found in the blood plasma.

Function

CD14 functions as a pattern recognition receptor (PRR) that binds to LPS, a component of the outer membrane of Gram-negative bacteria. Upon binding to LPS, CD14 interacts with Toll-like receptor 4 (TLR4) and MD-2, forming a complex that initiates downstream signaling pathways leading to the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-_B) and the production of cytokines.

Role in Immune Response

CD14 is essential for the recognition of bacterial infections and the subsequent activation of the immune response. It enhances the sensitivity of TLR4 to LPS, allowing for a rapid response to bacterial invasion. The activation of NF-_B leads to the production of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-_) and interleukin-6 (IL-6), which are crucial for the recruitment of immune cells to the site of infection.

Clinical Significance

Alterations in CD14 expression or function can have significant implications for human health. Overexpression of CD14 has been associated with increased susceptibility to sepsis, while deficiencies in CD14 can lead to impaired immune responses. CD14 polymorphisms have also been linked to various inflammatory diseases, including asthma and Crohn's disease.

Related Pages

• Toll-like receptor
• Innate immune system
• Lipopolysaccharide
• Macrophage
• Cytokine