SCD14 can be detected in normal plasma and cell supernatant. sCD14 may be derived from glycoprotein on the cell surface and released by enzymatic hydrolysis of GPI-anchored membrane protein by phospholipase or by protease digestion.

CD14 molecules can also exist in the form of soluble molecules in normal human plasma and in the culture supernatant of human monocytes and other cell lines. According to the different molecular weights and dynamics, CD14 has two forms: ① with different stimulants, such as phorbol ester (PMA) and INF- γ Or LPS can induce the detachment of GPI-anchored membrane-expressing CD14, producing CD14 with a relative molecular weight of 48000-49000. This detachment type may be regulated by membrane-bound serine protease. ② Some CD14 molecules separated from the attachment of GPI-anchored molecules and still retained their C-terminal precursor signal peptide, resulting in the production of sCD14 with a relative molecular weight of 55000~56000. This form of CD14 is stored in the cell and can be released spontaneously when the temperature changes briefly. This process does not change with the presence or absence of protease inhibitors.

The presence of sCD14 with a relative molecular weight of 55000 can be detected in patients with paroxysmal nocturnal hemoglobinuria (PNH), which is due to the defect of GPI synthesis and the inability of monocytes to express mCD14 molecule. The increased expression of sCD14 may compensate for the decreased expression of mCD14. In PNH patients, monocytes can bind LPS and react with sCD14. It is still unclear whether this two sCD14 have different biological effects. In the plasma of patients with septicemia, sCD14 with a relative molecular weight of 56000 increased, while there was no difference in the prognosis between the two types of sCD14 with a relative molecular weight of 56000 and 48000.