CD177 is a protein found on the surface of neutrophils, a type of white blood cell. It serves as a marker for certain neutrophil populations and is involved in various biological processes. Its study offers insights into immune function and disease states, including autoimmune disorders and certain cancers.
Understanding Neutrophils
Neutrophils are the most abundant white blood cell in humans, making up 40% to 70% of all white blood cells. They are a primary component of the innate immune system, acting as the body’s first line of defense against pathogens like bacteria and fungi. Produced in the bone marrow, they circulate in the bloodstream, ready to respond to infection or injury.
Neutrophils migrate to inflammation sites and combat microorganisms through phagocytosis, degranulation (releasing antimicrobial substances), and forming neutrophil extracellular traps (NETs) that ensnare and kill microbes.
How CD177 Influences Neutrophil Function
The CD177 protein is a glycosylphosphatidylinositol (GPI)-anchored protein found on the surface of a variable proportion of human neutrophils. It influences neutrophil functions, including activation, adhesion to blood vessel walls, and migration to inflammatory sites. CD177 associates with β2 integrins, which are cell adhesion molecules, and recognizes PECAM-1 on endothelial cells. Ligation of CD177 can impair the migration of CD177-positive neutrophils by enhancing their interaction with β2 integrins, affecting their adhesion and signaling.
CD177 and Disease Associations
CD177 has links with various disease states, particularly autoimmune disorders and inflammatory responses. It is a target antigen in ANCA-associated vasculitis (AAV), where autoantibodies (PR3-ANCA) bind to proteinase 3 (PR3) on the neutrophil surface. CD177 is co-expressed with PR3 on neutrophils, and the proportion of these CD177-positive/PR3-positive cells is often increased in AAV patients.
In inflammatory bowel disease (IBD), CD177 expression and the number of CD177-positive neutrophils are often elevated, relating to bactericidal activity, mucosal barrier repair, and inflammatory responses. CD177 levels are also elevated in acute pancreatitis, correlating with disease severity.
Beyond autoimmune and inflammatory conditions, CD177 shows associations with certain cancers. In some solid tumors like colorectal and gastric cancer, a higher density of CD177-positive neutrophils has been linked to a favorable prognosis. However, in lung adenocarcinoma, high density has been associated with shorter progression-free and overall survival, indicating a varied role depending on the cancer type.
Detecting CD177 and Its Clinical Value
Detection and measurement of CD177 on neutrophils are commonly performed using flow cytometry, a laboratory technique that analyzes cells as they flow through a laser beam. This method quantifies CD177-positive neutrophil populations and expression intensity.
The percentage of CD177-positive granulocytes can indicate various clinical conditions. For example, a decreased percentage is associated with myelodysplastic syndrome (MDS), where CD177 analysis enhances diagnostic sensitivity. CD177 also serves as a prognostic indicator in certain cancers; low expression in cervical cancer predicts poorer survival, while high expression in colorectal cancer may suggest a better prognosis.