Classification of a tumor antigen. Specific antigen
In some human tumors, studies specific antigen made some breakthroughs. For example, mutations in oncogenes and tumor suppressor gene product p21, p53 protein was found that certain virus-encoded tumor specific antigen, such as adult T cell leukemia virus HTLV-l-encoded tax antigen; not expressed in normal cells, tumor cells only activate the MAGE genes encoding melanoma antigens and some of the variability of growth factor receptors. It is characterized by three types of antigens: only in tumor tissues, can be shared by different tumors. Because some of them can specific, MHC restricted T lymphocytes by the form of recognition, so this kind of antigen in tumor biological therapy be closely watched.
2. Associated antigen
These antigens is characterized by the patients themselves do not produce an immune response to them, but can be prepared the amount of the corresponding monoclonal or polyclonal antibodies, immunological methods can be in the patient's serum or quantitative detection of tumor cells. Their level of concentration in the blood and cancer cells in volume. Common tumor-associated antigens:
Classification of tumor antigens, (1) alpha-fetoprotein (a-F etoprotein, AFP)
It consists of 590 amino acids, sugar 4% of the serum glycoprotein, molecular weight 6.9XI05Da. The protein in fetal development to six weeks when the began to appear, disappear after a week neonatal AFP. Adult blood very low, almost undetectable. According to AFP on the molecular structure of sugar-based differences, with the exogenous lectin (lentil lectin, LeA) binds can be divided into bound and non-bound AFP AFP. AFP serum of patients with primary liver cancer for the former; and benign liver disease, blood AFP mainly the latter. Determination of serum AFP commonly used radioimmunoassay and ELISA (ELISA) method. Normal human serum AFP value of 10 – 30ng / time, AFP twenty-three 400ng/ml can be used as a reference diagnosis of liver cancer. Analysis by AFP heterogeneity (LCA affinity method), and LCA with AFP> 25% of primary hepatocellular carcinoma when prompted.
Clinical Significance:
diagnosis of primary hepatocellular carcinoma with AFP. At present the majority view was that AEP> 300ng/ml and those who do not rule out continuing 4-8 weeks liver, low concentrations (50-200ng/m1) sustained (> February)-positive patients, should be regarded as high risk of liver cancer. Clinical, if the AFP> 400ng/ml can be diagnosed with primary liver cancer. Gonadal tumors, such as ovarian cancer, endometrial cancer, testicular cancer may also increase AFP can be used as diagnostic indicators of these tumors.
used to assess the efficacy and prognosis. If after resection of primary liver cancer without metastasis before surgery, radical surgery, the serum AFP in 2-4 weeks can be reduced to normal levels 50ng/ml), or down if the concentration did not fall after the re-rise, suggesting that diffuse of liver cancer or cancer recurrence. If in the course of postoperative chemotherapy after surgery to maintain the level of AFP content, showing a stable condition; fall show got better and sustained effect of poor did not fall. Although the diagnostic value of AFP has been affirmed, statistics show that the sensitivity of AFP for primary liver cancer, only 70% – 75%, there is still a considerable number of patients may be missed, the diagnosis of metastatic liver cancer even worse. Therefore, indicators of AFP negative patients with clinically suspected primary liver cancer data should be combined with other tests or the joint detection of multiple targets to compensate each other to reduce misdiagnosis.
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