CD14, also known as the LPS receptor, is a surface antigen belonging to the family of cell surface glycoproteins. It exists in two forms: membrane-bound CD14 (mCD14), which is anchored to the cell membrane via a glycosylphosphatidylinositol (GPI) tail, and soluble CD14 (sCD14), found in the plasma. CD14 is primarily expressed on monocytes, macrophages, and dendritic cells, and plays a critical role in the immune system by recognizing and binding to lipopolysaccharide (LPS) from Gram-negative bacteria, leading to cellular activation and the initiation of inflammatory responses.