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List at least four sources of foreign substances to which your body is regularly exposed.

-Antigens can enter the body through inhalation, ingestion, or injection. One is exposed to lactose and vitamins through ingestion, various gases through inhalation, and occasional vaccines through injection.

The challenge of the body with respect to foreign substances is greater than simply "keeping all of them out." How is this so?

-Because many exogenous antigens are essential, the body must determine whether or not the antigen should be allowed entry to cells or should be isolated and eliminated. APCs (antigen-presenting cells) and later helper T-cell must determine whether or not the exogenous antigen is harmful or not, this allows the body to avoid infection and obtain nutrients.

List three lines of biological defense against disease in order of their involvement. For each of the second and third lines of defense, name the types of body cells that are instrumental in the defense against foreign agents, and explain generally how these body cells usually overcome the invading cell or antigens

-The first line of defense is the skin and mucous membrane. These disable antigens from entering the body. The second line of defense involves an inflammatory response which is a rush of white blood cells, and phagocytes which engulf entering antigens. The third line of defense involves helper T-cells which determine whether or not an antigen is harmful, killer T-cells which destroy any antigens that have been marked by the last component; B-cells.

Explain each of the following observations:

Insect bites and other skin wounds often become inflamed and form an accumulation of white pus.

The body detects foreign invaders, and response with white blood cells (the inflammation) who begin to fight any antigens and possibly die (the pus).

The immune system has the capacity to distinguish "self" from foreign cells.

-The body only recognizes antigens with certain antibodies bonded to them as harmful, most self antigen’s antibodies are recognized as benign and left alone.

HIV (human immunodeficiency virus) usually has very deadly effects on an infected person.

-HIV infects white blood cells, which severely weakens the body’s immune system, rendering it quite susceptible to disease.

Certain cancerous cells are easier to "kill" by chemotherapy treatments than others.

-Chemotherapy targets cells that divide at certain rates (typically abnormally fast), when many non-cancerous cells in the body divide at a similar rate, those cells are likely to be killed off as well.

After recovery from a disease in which the immune system was involved, your body can develop active immunity.

-Your body can begin active immunity because of the production of memory B-cells. Which initiate a targeting of the harmful antigens and eliminate them quickly.


Malaria is a bacterial disease caused by the protozoan parasite; Plasmodium. Various forms of Plasmodium are considered a human pathogen, including but not limited to (there are at least 10 that can infect humans): Plasmodium vivax, Plasmodium ovale, Plasmodium falciparum, and Plasmodium malariae. Malaria is transmitted by mosquitos. When a mosquito bites an infected person, a small amount of blood that contains the malaria parasites is extracted.

After parasites develop within the mosquito for approximately one week, the infectious parasites are developed enough to afflict the mosquito’s victims. Once settled in the liver of it’s new host, the parasites begin to develop even further, and anywhere from two weeks to several months, the parasites begin to multiply within the red blood cells. These two attacks are separate. The exoerythrocytic phase is when the parasites infect the liver, and the erythrocytic phase involves the infection of the red blood cells. During the exoerythrocytic phase, the parasites rupture their liver host cells and are released into the blood, beginning the erythrocytic stage.

The parasite is incredibly protected from attack by the body’s immune system because throughout the remainder of it’s inhabitance, it resides within the liver and blood cells thus allowing it to remain relatively invisible to immune surveillance (such as being targeted by B-cells). The symptoms of malaria include shivering, fever, vomiting, joint pain, retinal damage, and convulsions. The combination of symptoms that is commonly found in malaria cases is an alternation between sudden coldness and a fever and sweating lasting from four to six hours. No clinical practice vaccine has been made available yet, however tolerance to the disease can be obtained when exposed to multiple strains of malaria.


- Coico, R., Sunshine, G., and Benjamin, E. (2003). “Immunology: A Short Course.” Pg. 48.

- Parham, P. (2005). The Immune System, Garland Science Publishing, New York, NY.

Trager W, Jensen JB (1976). "Human malaria parasites in continuous culture.". Science 193 (4254): 673–675

Sachs J, Malaney P (2002). "The economic and social burden of malaria". Nature 415 (6872): 680–5.