CD34 is a transmembrane glycoprotein primarily expressed on the surface of hematopoietic stem/progenitor cells, vascular endothelial cells, and certain stromal cells. Discovered in the 1980s, it belongs to the sialomucin family and functions as a cell-cell adhesion molecule, though its exact biological role remains partially unclear. Structurally, CD34 contains a heavily glycosylated extracellular domain, a single transmembrane region, and a cytoplasmic tail. Its expression is commonly associated with primitive cell populations, making it a key marker for identifying and isolating stem cells in research and clinical applications, such as hematopoietic stem cell transplantation.
CD34 antibodies, developed against specific epitopes of this protein, are widely used in flow cytometry, immunohistochemistry, and immunofluorescence to characterize cell populations. In diagnostics, CD34 immunostaining aids in identifying vascular tumors (e.g., angiosarcoma) and distinguishing certain soft tissue neoplasms (e.g., gastrointestinal stromal tumors from dermatofibrosarcoma protuberans). However, its expression isn't lineage-specific, requiring careful interpretation alongside other markers.
While CD34's role in cell adhesion, migration, and differentiation signaling is studied in contexts like vascular repair and cancer metastasis, its functional mechanisms remain an active research area. Variations in antibody clones (e.g., QBEnd/10. Class II/III epitopes) may yield differing staining patterns, necessitating validation for specific applications.