AFP - Alpha fetoprotein | Elisa - Clia - Antibody - Protein

Background

Alpha-fetoprotein (AFP) is a protein that is normally produced by the liver and yolk sac of a developing fetus. It is also produced in small quantities by the fetal gastrointestinal tract. AFP levels are typically high in the fetus, but they decrease rapidly after birth and remain low in healthy adults. AFP is considered a marker of fetal development. During pregnancy, AFP levels can be measured in the mother's blood or amniotic fluid as part of prenatal screening tests. Abnormal levels of AFP may indicate certain developmental abnormalities, such as neural tube defects (e.g., spina bifida) or chromosomal abnormalities (e.g., Down syndrome).Elevated levels of AFP in the blood can also be indicative of certain types of cancer, particularly liver cancer (hepatocellular carcinoma) and certain germ cell tumors. In patients with liver cancer, AFP levels may be used as a tumor marker to monitor disease progression and response to treatment. However, it's important to note that not all cases of liver cancer produce elevated AFP levels, and AFP levels can also be elevated in other conditions, such as cirrhosis and hepatitis.AFP testing is commonly used in clinical practice for various purposes:Prenatal Screening, AFP Cancer Diagnosis and Monitoring, and Monitoring Liver Disease

Protein Structure

AFP is a single-chain glycoprotein with a complex structure:

• Molecular weight: Approximately 70 kDa.
• Domains: It has three homologous domains similar to albumin, contributing to its structural stability and binding properties.
• Glycosylation sites: AFP is heavily glycosylated, with carbohydrate chains playing a role in its stability and function.

Classification and Subtypes

AFP belongs to the albumin gene family. Although AFP itself does not have distinct subtypes, its levels and glycoforms can vary significantly depending on the physiological and pathological conditions:

• Fetal AFP: Produced during fetal development.
• Adult AFP: Low levels are normally present in adults, with significant increases typically indicating pathological conditions.

Function and Biological Significance

AFP has several critical functions:

1. Fetal Development: AFP serves as a fetal plasma protein, analogous to adult albumin, helping in the transport of various substances such as hormones, fatty acids, and bilirubin.
2. Regulation of Cell Growth: AFP is involved in the regulation of cell proliferation and differentiation during fetal development.
3. Immune Modulation: AFP has immunosuppressive properties, which may protect the fetus from maternal immune responses.

Interactions

1. Estrogens: AFP binds estrogens, preventing their excessive action during fetal development.
2. Fatty Acids and Bilirubin: Similar to albumin, AFP binds and transports fatty acids and bilirubin, protecting fetal tissues from toxicity.
3. Growth Factors: AFP interacts with various growth factors, influencing cell growth and differentiation.

Clinical Significance

1.-Tumor Marker: AFP is a well-established tumor marker for certain cancers:

• Hepatocellular Carcinoma (HCC): Elevated AFP levels are commonly associated with HCC, making it a key diagnostic and prognostic marker.
• Germ Cell Tumors: AFP is also elevated in certain germ cell tumors, such as yolk sac tumors and non-seminomatous testicular cancer.

2.-Prenatal Screening: AFP levels are measured during pregnancy as part of screening tests for fetal abnormalities:

• Neural Tube Defects: Elevated AFP levels in maternal serum or amniotic fluid can indicate neural tube defects like spina bifida.
• Down Syndrome: Lower-than-normal AFP levels can be associated with Down syndrome.

3.-Liver Diseases: Elevated AFP can be indicative of chronic liver diseases, such as cirrhosis and hepatitis, although it is less specific than in cancer.

Summary

Alpha-fetoprotein (AFP) is a crucial fetal plasma protein involved in the transport of various substances, regulation of cell growth, and immune modulation during development. Clinically, AFP is a significant biomarker for certain cancers, particularly hepatocellular carcinoma, and is widely used in prenatal screening for fetal abnormalities. Understanding AFP's roles and interactions enhances its utility in both diagnostic and prognostic contexts across various medical fields.