CD163 is a membrane protein that is produced exclusively on the cells of the immune system, i.e. monocytes and macrophages. If these come into contact with inflammation-promoting stimuli, for instance, bacterial molecules, CD163 is enzymatically cleaved off of the immune cell membrane, which results in the formation of soluble CD163 (sCD163). In glomerulonephritis, macrophages migrate into the tissue and release sCD163 into the urine via the Bowman’s capsule. The biomarker can then be measured in the urine.
The more serious the inflammation, the more macrophages migrate into the tissue. This means that the concentration of sCD163 in urine directly provides information about the severity of the glomerulonephritis. The sCD163 level correlates with the disease activity. The higher its concentration, the more severe the inflammation.
The sCD163 ELISA (European patent (EP3283889)) is particularly suited for monitoring patients with diagnosed AAV with renal involvement. Contrary to systemic inflammation markers, the sCD163 level is a specific indicator of renal inflammation and reacts quickly under treatment or in case of fluctuations in the inflammatory activity.
If, during regular testing, the sCD163 concentrations increase again after having been normal for some time, this can point to a renewed outbreak of the kidney inflammation. The treatment can then be adjusted at an early stage, preventing irreversible kidney damage in the patient.