Good Essay1 Essay Example

Discussion Questions

Discussion Questions:

Humoral immunity is one in which, the immune attack is mediated by macromolecules called antibodies. The foreign agents dealt by them are called antigens. The antigen –antibody reactions are highly specific. The reaction is classified into many types based on the physical properties of the antigen (soluble or insoluble) and the kind of antibody (IgG, IgM, etc) involved. When bivalent (IgG) or multivalent (IgM) antibodies binds to many antigens molecules, they are brought together in space and adhere to each other forming agglutinins. IgM is good at causing agglutination because they have more antigen binding site. Agglutination can be observed in mismatched blood transfusion. Precipitation or flocculation occurs when antibodies interact with insoluble antigens. When the antigens and antibodies are at optimum levels we notice maximum precipitation. If the antigens are excess and antibodies are very less or the vice versa, insufficient lattice formation takes place and the precipitate is not visible. Immuno-electrophoresis, radical immunodiffusion, counter current electrophoresis are some of the applications of precipitation reaction. Most often antigen-antibody complex may not be solely sufficient to eliminate an infection. This complex activates a cascade of enzymes called complements, which when activated form the membrane attack complex that destroys the foreign cells. Another important reaction between antigen and antibody is called opsonisation and this helps in phagocytosis. The phagocytes recognize the Fc portion on the antibody and are thus bind to the antigen –antibody complex. The antigen –antibody interact by weak reversible bonds and not by forming covalent bonds. The strength of the bond can be increased by increasing the number of weak bonds formed. Affinity and avidity are important determinants of antigen-antibody interaction. Multivalent antigens with many repetitive epitopes for binding by many antibodies or multivalent antibodies with many binding site that bind to many antigen, enhance the avidity of the interaction. On the other hand, the degree of close fit between the epitope of the antigen and the antitope of the antibody decides, the affinity of the antibody –antigen interaction.

Bibliography:

1. Paul, W. (1993). Fundamental Immunology. New York: Raven Press
2. Stanley, J. (2002). Essentials of immunology & serology. Albany, NY: Delmar Thomson Learning.
Essay2
Diagnosis of parasitic infection is usually done by direct examination of faeces, urine, blood and tissues for the parasite and their ova. Indirect serological methods like ELISA, immunohistochemistry, PCR, indirect florescent antibody techniques, etc are also used for sensitive and efficient diagnosis. Currently there is no one technique which can replace the need for different sample specific techniques used in Parasitology. The choice of deciding which technique to employ depends on the clinical signs, patient’s history, and the type of parasite to be identified. Oocysts or eggs of some parasites like coccidia and helminthes are not seen in blood and a fecal examination may be necessary to make a diagnosis. Like wise Schistosoma eggs are quite often seen in urine and not in the blood. Stools/ faeces examination and endoscopy are commonly used to identify intestinal parasites. The case may differ for extra intestinal parasite. Blood parasites like Malaria, Theileria, Babesia, Anaplasmas, Ehrlichia, Trypanosoma and most types of Filaria, are diagnosed by blood examination. Blood smear or buffy coat smear stained with Giemsa, Diff-Quick, or QBC are commonly used to diagnose these diseases. Skin scrapping treated with 10% KOH is used for diagnosis of mites. Muscle biopsies or tissue examination may be necessary for detection of Toxoplama gondi and Trichinella infection. Some serological techniques like ELISA were also found useful in diagnosis of these parasites. Certain intestinal parasites have their extra intestinal stages in other tissues; neurocysticercosis in humans is due to larval cyst of Taenia solium in neural tissues. In such cases diagnosis can be made by MRI or CT scan. While adult tape worm infest the small intestine, their larval stage can be seen in other organs. Hydatid cyst is the larval stage of Echinococcus granulosus. Man is an intermediate host and hydatidosis in different tissues is common when infected with this parasite. Diagnosis is done by whole body scan and demonstration of protoscoliosis in the operated cyst. Serological techniques have proven to be less invasive in the sensitive diagnosis of many extraintestinal parasites.
Bibliography:
1. Gracia,L. (2001). Diagnostic medical parasitology. Washington, D.C.: ASM Press.
2. Markell,E., Voge, M., & John, D. (1992). Medical parasitology. Philadelphia: Saunders.