Biomedical Importance Agglutinogen - Essay Example

Edited Hematology Rh factor- It is another agglutinogen that is found in the RBCs and were discovered by Landsteiner and Wiener in 1940. The agglutinogen was so named as it was found from the Rhesus monkey and is present in around 85% of white people. It has also been found in the RBCs of Indian and Ceylonese population to the tune of around 95%. For this agglutinogen there is no corresponding agglutinin in the human plasma. There are six Rh agglutinogens namely the C,c,D,d,E and e. Of these 6 agglutinogens the D and d are the most common and provides a combination of three groups D,Dd and d. D is inherited as the Mendelian dominant trait while d is inherited as the recessive trait. The RBCs which bear the D and Dd isotypes are referred to as Rh+ individuals and persons having the d isotype are referred to as Rh- individuals. Almost all of the Rh+ people have the D isotype and similarly the Rh- individuals have the d isotype. When the Rh+ blood is transfused to an Rh- person then anti-Rh factor will develop in the patient’s blood within 12 days. If there is a second transfusion of the same blood (Rh+ blood) to that person then cross reaction with Rh factor and anti-Rh factor will cause agglutination reactions leading to hemolytic diseases of adults and newborn. If the mother is rhesus negative and the fetus is rhesus positive (the RBC contains Rhesus antigen inherited from a rhesus positive father), then antibodies will be formed against the rhesus antigen (in the fetus) and will cross the placenta and enter the mother’s blood. In the first pregnancy there will be no issues but during the second pregnancy these antibodies will cross the placenta and cross react with the Rhesus antigens of the fetus carried during the second pregnancy and cause agglutination reactions. This will cause erythroblastosis fetalis leading to hemolytic anemia and sometimes deposition of unconjugated bilirubin (derived from the breakdown of hemoglobin from the lysis of RBC’s) in the basal ganglia leading to neural deficits (Chatterjee, 2004). 2. All the six Rh agglutinogens namely the C, c, D, d, E and e are involved in the hemolytic reactions and are of the delayed type. Although routine blood group tests has eliminated the risk of compatibility of RhD isotype but the other isotypes may lead to sensitization in cases of diseases like sickle cell anemia. This disease is prevalent in blacks who express the E antigen and hence produce the anti-E agglutinins which lead to difficulties of donor selection in them for transfusion purposes as in sickle cell anemia where blood transfusions are routinely required. 3. Most of the hemolytic diseases of the newborn (HDN) are caused by the anti-D antibodies which are formed to the RhD agglutinogen. However routine screening of blood types of at risk pregnant patients have eliminated the risk of Rh incompatibility in them. Normally the problem arises the mother is rhesus negative and the fetus is rhesus positive (the RBC contains Rhesus antigen inherited from a rhesus positive father), then antibodies will be formed against the rhesus antigen ( in the fetus) and will cross the placenta and enter the mother’s blood. In the first pregnancy there will be no issues but during the second pregnancy these antibodies will cross the placenta and cross react with the Rhesus antigens of the fetus carried during the second pregnancy and cause agglutination reactions. This will cause erythroblastosis fetalis leading to hemolytic anemia and sometimes deposition of unconjugated bilirubin (derived from the breakdown of hemoglobin from the lysis of RBC’s) in the basal ganglia leading to neural deficits (Chatterjee, 2004).Apart from the anti-D antibodies , the anti-C antibodies are also responsible for the HDN.(Chatterjee, 2004). 4. Various methods are in use for the collection of smears from the cervical region of the vagina for the purpose of Pap smear testing: i. Conventional Pap smear test In the conventional pap smear test a speculum is inserted through the vaginal canal to held it open and gain access to the cervical region where the sample of epithelial cells are collected with the help of a endocervical brush or spatula. The smear of cells are obtained on the slide and viewed under a microscope for the detection of abnormality caused by the human papilloma virus. However in the conventional test there can be overcrowding of cells when the smear is drawn up on the slides leading to deceased resolution of detection (Davey et al, 2007). ii. Liquid Based Cytology Tests This is done with the help of Thin Prep Pap test and thin prep imaging system which is based on the Liquid Based Cytology where the cells collected from the cervix is preserved in a liquid and a machine is used to remove the excess blood and mucosal cells which may hamper the resolution of the image. A cutting edge computerized system is used to detect the cellular abnormalities. The thin prep system has been found to be 27% more effective in determining the precancerous cervical tissues than the conventional Pap smear test (Davey et al, 2007). Keratins are a group of fibrous proteins that makes up the intermediate filaments that comprises the cytoskeleton of the cells. The cell specific cytokeratins type II is found in two forms acidic and basic. The cell specific keratins are found in the epithelial tissues which lines the cavities of internal organs like the blood vessels and the urogenital tracts. The genes that encode these proteins are located in chromosome 12 and 13. There are various isotypes of cytokeratins which are classified according to their molecular weight and their exclusivity in the tissue found. Keratin 7 is on form of type II cytokeratins that is expressed by the epithelial tissues lining the internal organs like lungs and the breast while it is not expressed by the prostrate gland or colon. Thus keratin 7 is used as a diagnostic tool to differentiate between ovarian and colorectal carcinomas (Schweiser et al, 2006). However Keratin 20 is a type I cytokeratin expressed by enterocytes and the goblet cells. Thus this protein are expressed in carcinomas of the colon or transitional epithelial cells but is not expressed in patients with lung or ovarian cancer. Hence these two cytokeratins are used to differentiate the carcinomas according to their organ of origin. Thus the cytokeratins are a component of the intermediate filaments and is encoded by around 30 genes. Each cytokeratin molecule exists in a tetrameric form and each monomer comprises of a central alpha helical domain while the amino and carboxyl terminals are flanked by non alpha helical domains (Schweiser et al, 2006). Additional Reference Davey E, et al (2007). Accuracy of reading liquid based cytology slides using the Thin Prep Imager compared with conventional cytology: prospective study. British Medical Journal; 335 (7609):28 Read More