HB+Immune+System

=PATHOGENS=

What is a pathogen?

 * A pathogen is a human infectious disease that are caused by bacteria and viruses.

What are the body's three lines of defense against pathogens?

 * Barriers to entry such as the skin and mucous membranes of body cavities. They prevent pathogens from gaining entrance into the body.
 * First responders, such as the phagocytic white blood cells, act to prevent an infection after an invasion has occured.
 * Specific defenses overcome an infection by killing the particular disease-causing agent that has entered the body. Specific defenses also protect us against cancer.

Write a one paragraph summary of bacteria.

 * Bacteria are single celled prokaryotes that lack a nucleus. Bacteria take form in three different shapes. Bacillus, rod shape. Coccus, spherical shape. And Spirillum, curved shape. Bacteria live and produce independently of host cells and cause disease by multiplying in hosts and also by producing toxins. The walls of of some bacteria are surrounded by a capsule, which allows the bacteria to stick to surfaces such as teeth. They also prevent phagocytic white blood cells from taking them up and destroying them.

Write a one paragraph summary of viruses.

 * A virus is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell. Each viral particle, or virion, consists of genetic material, DNA or RNA, within a protective protein coat called a capsid. The capsid shape varies from simple helical and icosahedral (polyhedral or near-spherical) forms, to more complex structures with tails or an envelope. Viruses infect cellular life forms and are grouped into animal, plant and bacterial types, according to the type of host infected. Biologists debate whether or not viruses are living organisms. Some consider them non-living as they do not meet the criteria of the definition of life. For example, unlike most organisms, viruses do not have cells. However, viruses have genes and evolve by natural selection. Others have described them as organisms at the edge of life. Viral infections in human and animal hosts usually result in an immune response and disease. Often, a virus is completely eliminated by the immune system. Antibiotics have no effect on viruses, but antiviral drugs have been developed to treat life-threatening infections. Vaccines that produce lifelong immunity can prevent viral infections.

What is an emerging virus?
=IMMUNE SYSTEM=
 * Emerging viruses emerge by being transported from one location to another where it has never been before. Flu strains move from Southeast Asia to the United States every year. The West Nile virus is making headlines because it has changed its range, being transported into the United States and taking hold in bird and mosquito populations. SARS (severe acute respiratory syndrome) was transported from Southeast Asia to Toronto, Canada. Viruses can emerge because of the inability of the immune system to recognize a change in the virus that allows it to cause disease. Viruses that continually change their "faces", such as HIV, are far more difficult to eradicate.

What is an antibody? What do they do?

 * An antibody is a protein produced in response to the presence of an antigen, each antibody combines with a specific antigen.

What is B Cell?

 * The B Cell produces plasma cells and memory cells. Plasma cells produce specific antibodies and memory cells are ready to produce antibodies in the future.

What is a Cytotoxic T Cell?

 * A cytotoxic T Cell kills virus-infected cells and cancer cells.

What is a Helper T Cell?

 * A Helper T Cell regulates immunity.

What is an antigen? How does the body respond to an antigen?

 * An antigen is a foreign substance, which is usually a protein or a polysaccharide, that stimulates the immune system to produce antibodies

SOURCES: wikipedia