An antibody designed to detect Cytokeratin 18 (CK18) is a specialized biological tool. It precisely identifies the CK18 protein within the human body, allowing for its localization and quantification. This aids in understanding normal cell function and changes associated with various health conditions, particularly in epithelial cell biology.
The Target Protein Cytokeratin 18
Cytokeratin 18 (CK18) is an intermediate filament protein, part of the cell’s internal scaffolding known as the cytoskeleton. These filaments provide structural support and mechanical resilience to cells. CK18 is a type I (acidic) cytokeratin that pairs with Cytokeratin 8 (a type II, basic keratin) to form stable heterodimers, creating a robust network within the cell’s cytoplasm.
CK18 is predominantly found in simple, single-layered epithelial cells, which line many internal organs and body cavities. Examples include the liver, gastrointestinal tract, pancreas, and lungs. CK18 stabilizes epithelial cell structure and function. It also contributes to the cell’s ability to manage stress and respond to programmed cell death.
Mechanism of Antibody Detection
The CK18 antibody is a Y-shaped protein engineered to bind to a specific region on the CK18 protein, known as an epitope or antigen. When the antibody encounters its target, it forms a complex, allowing researchers to pinpoint CK18 within a sample.
This antibody detects both intact CK18 protein and specific fragments. These fragments are generated when a cell undergoes programmed cell death, also known as apoptosis. During apoptosis, cellular enzymes called caspases cleave the full-length CK18 protein, exposing new epitopes. Detecting these caspase-cleaved fragments allows for measurement of cell death rates.
Clinical Significance and Diagnostic Use
The detection of CK18, particularly its fragmented forms, is important in medicine as a biomarker. A biomarker is a measurable substance in the body that indicates a biological state, disease, or response to treatment. When epithelial cells undergo programmed cell death, they release CK18 fragments into the bloodstream, making them quantifiable in bodily fluids. Measuring these fragments with CK18 antibodies provides insights into cell death in various tissues.
A primary clinical application for CK18 fragment detection is in liver disease, particularly non-alcoholic steatohepatitis (NASH). Elevated levels of caspase-cleaved CK18 fragments in the blood are associated with increased liver cell death in NASH patients. This makes CK18 a useful non-invasive indicator for monitoring disease progression, assessing liver damage severity, and evaluating therapy effectiveness for conditions like NASH and cirrhosis. A rise in CK18 levels can indicate more active liver inflammation and damage, distinguishing NASH from simpler fatty liver conditions.
In oncology, CK18 also serves as a tumor marker for certain epithelial cell cancers, known as carcinomas. These include breast, prostate, and lung cancers, where changes in CK18 expression or release can reflect disease progression. Monitoring CK18 levels can assist in tracking cancer treatment response or detecting recurrence. CK18 is often used with other diagnostic tests and imaging techniques for a comprehensive patient assessment.
Laboratory Techniques Employing the Antibody
The CK18 antibody is used in several laboratory techniques to detect and quantify the protein. One method is the Enzyme-Linked Immunosorbent Assay (ELISA). In ELISA, the CK18 antibody captures and measures the concentration of CK18 fragments in liquid samples. This technique yields a quantitative result, useful for monitoring disease activity over time.
Another technique is Immunohistochemistry (IHC). IHC is applied to solid tissue samples to visualize the presence and location of CK18 within cellular structures. In this method, the CK18 antibody is linked to a detectable label. When applied to tissue, the antibody binds to CK18, and the label allows pathologists to see where the protein is located and its abundance within the tissue architecture. This provides qualitative information, showing the distribution of CK18 within cells and tissues.