1. By: Martin Naranjo and Juan Jacobo Gachan

2.  An agent of disease or in other words a disease producer.  The term pathogen most commonly refers to an organism or a virus that causes a disease.  These include bacteria (such as staph), viruses (such as HIV), and fungi (such as yeast).  Less commonly, pathogen refers to a noninfectious agent of disease such as a chemical.

3.  Antibiotics are drugs produced by microorganisms which kill or slow or control the growth of other microorganisms like bacteria by blocking specific metabolic pathways within the cell.  Since bacteria are so different to human cells, antibiotics can be taken by humans to kill bacteria without harming the human cells.  Antibiotics block metabolic pathways of bacteria, inhibiting cell wall formation and protein synthesis, resulting in the death of foreign bacteria.  Viruses on the other hand are different as they do not carry out many metabolic processes themselves.  Viruses are not alive and instead they rely and utilize the organisms host cells to replicate which are not targeted by antibiotics.  Therefore viruses cannot be treated with antibiotics as it is impossible to harm the virus without harming the human cells.

4.  Skin and mucous membranes act as barriers against pathogens.  The skin and mucous membranes form a barrier that prevents most pathogens from entering the body.  The other layers of the skin are tough and form a physical barrier.  These dry, keratinized layers of skin discourage pathogen growth.  The skin also produces a thin layer of acid and oils.  Mucus contain an enzyme called lysozyme which kills bacteria.

5.  Phagocytes are a type of leucocytes which ingest and destroy foreign matter through phagocytosis.  They can easily move through the walls of blood capillaries and the place in which there is an infection.  A phagocyte comes in contact with pathogen cells and does not recognize the glycoprotein structure on its cell wall.  The pathogen is then ingested through endocytosis and plasma membrane forms around pathogen.  Pathogen vacuole then binds with lysosome containing digestive enzymes which break down the pathogen.  Large numbers of phagocytes form pus.

6.  Antigens are macromolecules that elicit an immune response by lymphocytes.  Antibodies are proteins secreted by plasma cells that bind to a particular antigen and mark it for elimination.

7.  Antibodies are made by lymphocytes, which recognize an enormous number of antigens, but each individual cell recognizes only one type of antigen.  Each lymphocyte puts some of the antibody that it makes into its cell surface with the antigen-combining site projecting outwards.  When a pathogen enters the body, its antigens bind to the antibodies in the cell surface of one type of lymphocyte.  The selected lymphocyte proliferates to give rise to a clone of identical cells bearing receptors for the selecting antigen.  Some of the cells develop into short-lived plasma cells that secrete antibody specific for the antigen.  Others develop into long-lived memory cells that can respond rapidly upon subsequent exposure to the same antigen.

8.  HIV attacks T-cells which are part of the immune system that are important for the formation of Beta lymphocytes.  The virus enters the T-Cells and replicates there.  As reproduction increases, the cell breaks up and the virus RNA is spread to other T-cells.  The virus keeps infecting and killing other T-cells, paralyzing the immune system.  This enables other organisms usually kept under control by the immune system to be able to affect the body.

9.  The basic cause of AIDS is that the HIV retro-virus develops further enough to change into AIDS.  HIV doesn’t survive outside of the body and can’t easily pass through the skin.

10.  Transmission involves the transfer of body fluids from an infected person to an uninfected one.  Through small cuts or tears in the vagina, penis, mouth or intestine during vaginal, anal or oral sex.  In traces of blood on a hypodermic needle that is shared by intravenous drug abusers.  Across the placenta from a mother to a baby, or through cuts during childbirth or in milk during breast feeding.  In transfused blood or with blood products such as Factor VIII used to treat hemophiliacs.

11.  Friends and families suffer grief.  Families become poorer if the individual with AIDS was the wage earner and is refused life insurance.  Individuals infected with HIV may become stigmatized and not find partners, housing or employment.  Sexual activity in a population may be reduced because of the fear of AIDS.