Free Biology Essay Example

Essay 1. Immune Systems

There are two major groups of foreign substances and microscopic organisms that the immune system of the body could distinguished. The first group are the antigens that are freely moving around the body which includes viruses and foreign cells. The second group are the cells displaying aberrant major histocompatibility complex (MHC) proteins (Brito & Hinton, 1993). These cells includes self-cells which are invaded by the tumor cells and pathogens. In general, humoral immune response recognizes the antigens that are freely circulating around the body while the cell-mediated response recognizes the cells displaying aberrant MHC proteins (Rosenberg & Gallin, 1999).
The humoral immunity response is mediated by the macromolecules such as antibodies and complement proteins which are secreted extracellular fluids. It involves recognizing the antigens that are circulating in the blood (Brito & Hinton, 1993). The first step in the humoral immunity response is the biding of the antigens to the B cells. Then the B cells are co-stimulated by the helper T cells. The B cell proliferation is only initiated when the both the co-stimulator and the antigen activate the B cells. The B cells proliferate produces the plasma cells that composes the antibodies which are specific to identical antigen (Cowan, 2012). These antibodies are released to the blood to bind to the antigen and stopped their reactions. To provide the future immunity to the specific antigen, the memory cells are also produced by the B cells (Rosenberg & Gallin, 1999).
The cellular immunity response involves production of phagocytes and T-lymphocytes to response to the antigen displaying aberrant MHC proteins. The first step involves binding of the antigen displaying aberrant MHC proteins to the T cells. The activation of the T cells are co-stimulated by the interleukins which are produced by the helper T cells or the antigen itself. There are two chain of events that could occur in the cell-mediated response depending on the type of the antigen. If the cellular immunity response recognizes endogenous antigen or MHC-I, the T cells proliferate activating cytotoxic T cells (Cowan, 2012). These cells destroy the antigens displaying aberrant MHC proteins. If the cellular immunity response recognize the exogenous antigen or MHC-II, the T cells activates helped T cells. The helper T cells stimulates the B cells to produce the antibodies to destroy the antigens displaying aberrant MHC proteins (Brito & Hinton, 1993).
In general, the major difference between the two immunity responses is that the humoral response defends the body from the bacteria and the viruses while the cell-mediated response protects the body from the other pathogens such as protozoa and fungi. The humoral response involves B-lymphocytes while the cellular response involves T-Lymphocytes. The cellular immunity response could provide the body the immunity from cancer unlike the humoral immunity response. Lastly, the cellular immunity response could also respond with the transplant cells unlike the humoral immunity response (Brito & Hinton, 1993).
The immunodeficiency diseases could compromise the functions of both the humoral and the cellular immunity response. An example of the immunodeficiency disease that could compromise the humoral response is the Agammaglobulinemia. It is a genetic disorder and disease that affects mutation of the B cells. The interaction of B cells and T cells in the humoral immunity response is compromised due to the maturation and mutation of the B cells in the Agammaglobulinemia (Rosenberg & Gallin, 1999). An example of the immunodeficiency disease that could compromise the cellular response is the DiGeorge Anomaly. It involves not having a thymus or underdeveloped thymus which produce the T lymphocytes. The deficient T lymphocytes could compromise the functions of the cell-mediated immunity response (Brito & Hinton, 1993).

Essay 2. Organisms Causing Parasitic Disease

A parasite is a foreign organism living in the body of the host organism and causing harm to it. Parasites are dependent to the host for their survival, reproduction and growth. In general, parasites could not live alone without their host organism (Cowan, 2012). They are usually smaller than the host organisms which uses their strength for the benefit of the parasites. There are three main classes of parasitic organisms that could cause diseases in the human body which are protozoa, helminths and ecto-parasites (Chandler & Clark, 1976).
Protozoa are single-celled organisms which are able to multiply and survive inside the human body. They could provide serious infections and diseases to humans which usually develops from a single organism (Cowan, 2012). Protozoa could enter the human body from the fecal-oral route which could cause malaria, amoebiasis and other diseases. The protozoa that causes the malaria is the plasmodium while the amoeba causes the amoebiasis. Other types of protozoa are the Sarcodina, Mastigophora, Ciliophora and Sporozoa (Chandler & Clark, 1976).
Another type of parasitic organisms that causes diseases are the Helminths. Helminths are large multicellular organisms which are commonly known as parasitic worms. There are three main types of helminths which are flat-worms, thorny-headed worms and roundworms. An example of flat-worms are tapeworms which could cause intestinal infections. Thorny-headed worms are adult form of helminths which are residing at the gastrointestinal tracts of the human body. The roundworms such as ascaris and hookworms could rupture the intestinal tracts and cause infections (Chandler & Clark, 1976).
The last type of the parasitic organisms are the ecto-parasites or arthropods. They are large multicellular organisms which includes insects and arachnids. The insect itself is not the parasite but it carries the antigens or foreign substances that could cause diseases in humans. One major example of ecto-parasite is the mosquito which carries many types of human diseases. There are parasites that also live in the external parts of the human bodies such as ticks and fleas which could cause infections and allergies (Chandler & Clark, 1976).
The pathogenic protozoa could enter the human body and infect the cells especially the blood cells to survive. There are two types of pathways that the pathogenic protozoa could use to enter the host’s cells which are receptor-mediated endocytosis and phagocytosis. In the receptor-mediated endocytosis, the protozoa recognizes the protein in the surface of the host cell. The protozoa then activates the surface protein which causes the host cell to engulf the protozoa and absorbs its molecules (Chandler & Clark, 1976). The cell’s protein is destroyed and the protozoa produces the pathogens that induce the infections or diseases. The second path is through the phagocytosis which the protozoa activates the pathogens that is engulfed by the host cells. The protozoa then survives through the nutrients that the host cell provides due to the engulfed pathogens (Cowan, 2012).
There are three major methods in establishing a laboratory diagnosis of an intestinal parasitic infection (Cowan, 2012). First is the fecal exam or also known as the ova and parasite test. In this method, the stool is collected for several days or hours and examine if there are ova or eggs of the parasites. This test uses preservative fluids in order to maintain the possible parasitic eggs. The second method is the endoscopy or colonoscopy. It involves using tubes to examine the mouth (endoscopy) or the rectum (colonoscopy). The objective of the test is to examine the internal organs if there are living parasites that causes the symptoms or signs or infection. The last method for establishing a laboratory diagnosis of an intestinal parasitic infection is the blood method. This test includes examining blood samples for signs of parasites which includes blood smear and serology (Chandler & Clark, 1976).

References:

Brito, J., & Hinton, M. (1993). The humoral and cellular mediated immune response of young chicken to Salmonella typhimurium and S. kedougou. Immunology Today, 16(1), 21-45
Chandler, C., & Clark P. (1976) Introduction to parasitology. 20th edition John Wiley and Sons Inc.,
Cowan, M. (2012). Microbiology: A Systems Approach. 3rd ed. McGraw-Hill
Rosenberg, H., & Gallin, J. (1999). Fundamental Immunology. 4th ed. Philadelphia: Lippencott-Raven Publishing.