(1) Explain how the human defense system works, using the idea of the three lines of defense.

The immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection.

external image figure61.jpg
"6. Autoimmune Diseases and the Promise of Stem Cell-Based Therapies [Stem Cell Information]." NIH Stem Cell Information Home Page. Web. 30 May 2011. <http://stemcells.nih.gov/info/scireport/chapter6.asp>.

Purpose of each type of immunity
1st line of defence
Innate immunity
2nd line of defence
Adaptive immunity
3rd line of defence
Passive and Active immunity
The innate immunity system is the basic resistance the body possesses against diseases and infections. It acts as the 1st line of defence, preventing disease-causing microbes called pathogens from entering the body. This system consists of physical barriers such as the skin or the mucous lining.
The adaptive immunity system protects the body from re-exposure to a pathogen that already attacked the body once before. This system develops as people are exposed to more diseases or as people become immunized against diseases by vaccinations. Cells that are responsible for this include white blood cells called macrophages and granulocytes or natural killer (NK) cells
The passive immunity system manufactures antibodies called lymphocytes (particularly the B cells and T cells) that destroy pathogens such as virus-infected cells or other damaged, dysfunctional cells.
Differences between the first types of immunity

1st line of defence
Innate immunity
2nd line of defence
Adaptive immunity
Reaction rate to invading organism
This type of immunity is always ready to do their job when they detect infection.
This type of immunity takes some time before it can react.
Response specificity
Non-specific
Specific
This type of immunity serves as a barrier that is not specific in what it blocks. It does not antigen-specific and reacts well with different organisms alike.
The lymphocytes involved in this type of immunity identify specific pathogens that have been encountered before. The lymphocytes then make specific antibodies for those pathogens.
Immunological memory
No
Yes
This type of immunity does not exhibit immunological memory.
This type of immunity can remember how to respond to pathogens that it has encountered before, hence its name “adaptive” immunity.


Make sure your answer includes
§ What each line is
§ What each line does
§ Examples of each line AND how they work (brief outline only
§ Whether each line is specific or non-specific (& maybe what this means)
§ Read other groups work and create links to their work from yours


HINT: Maybe a table is a good way to present this information


(2) Explain how your body can recognize foreign materials and invaders when they enter your body.


Make sure your answer includes
§ The name of the molecules that are recognized, and what they are.
§ What part of your body recognizes them
§ How this system works
§ What happens when it goes wrong, with a brief example (brief)


(3) Make sure you have explained the processes of phagocytosis and immunity in your work –– YouTube videos may be a great way to explain…


HINT: be careful to organize this section well. It should not just be a random series in info. You may well choose to incorporate your responses to questions (4) and (5) in your question three response