Cytokeratin 19 (CK19) is a member of the intermediate filament protein family, primarily expressed in epithelial cells, where it contributes to structural integrity and cellular mechanical stability. As a low molecular weight keratin, CK19 is predominantly found in simple and glandular epithelia, such as those in the liver, pancreas, and respiratory tract, as well as in basal layers of stratified epithelia. Its expression is tightly regulated during development and tissue differentiation, making it a valuable marker for identifying epithelial cell lineages.
Antibodies targeting CK19 are widely used in research and diagnostics to detect epithelial-derived cells, particularly in cancer pathology. For instance, CK19 immunohistochemistry helps distinguish carcinomas from non-epithelial tumors and is critical in identifying metastatic cells in lymph nodes or circulating tumor cells (CTCs). In clinical settings, CK19 antibodies aid in diagnosing malignancies like breast, lung, and colorectal cancers. Notably, CK19 is a key biomarker in hepatocellular carcinoma (HCC) and cholangiocarcinoma, where its overexpression correlates with tumor progression and poor prognosis.
Additionally, CK19 antibodies are employed in studying epithelial-mesenchymal transition (EMT) and cancer stem cells, as CK19 expression may reflect cellular plasticity. However, interpretation requires caution, as CK19 can be detected in benign conditions (e.g., reactive epithelial proliferations) and non-neoplastic cells. Techniques like immunohistochemistry (IHC), Western blotting, and immunofluorescence rely on CK19-specific antibodies, underscoring their versatility in both basic research and clinical applications. Overall, CK19 antibodies remain indispensable tools for exploring epithelial biology and improving cancer diagnostics.