CD109 is a glycosylphosphatidylinositol (GPI)-anchored cell surface glycoprotein belonging to the complement regulatory protein family, also recognized as a TGF-β co-receptor. Initially identified in activated T-cells and platelets, it is broadly expressed in endothelial cells, immune cells, and certain epithelial tissues. CD109 plays multifaceted roles in regulating TGF-β signaling, cell adhesion, and immune responses. Its dual function includes both enhancing and suppressing TGF-β activity depending on cellular context, impacting processes like angiogenesis, fibrosis, and tumor progression. Dysregulated CD109 expression is implicated in cancers (e.g., squamous cell carcinoma, glioblastoma), inflammatory disorders, and psoriasis, often correlating with disease aggressiveness or poor prognosis.
CD109 antibodies are essential tools for studying its biological functions and clinical relevance. They enable detection of CD109 expression in tissues or cells via techniques like flow cytometry, immunohistochemistry, and Western blot. Specific antibody clones (e.g., TEA 2/16. H-130) target distinct epitopes, aiding in functional studies such as ligand-receptor interaction analysis or TGF-β pathway modulation. Recent research highlights CD109 antibodies in therapeutic exploration, including antibody-drug conjugates or immune checkpoint targeting. However, challenges remain in standardizing assays due to CD109's complex post-translational modifications and variable shedding from cell membranes. Ongoing studies aim to clarify its context-dependent roles and validate its utility as a diagnostic/prognostic biomarker or therapeutic target.