E Onyane Bo Ist: Dr. G Hitapha Munolo Im Dr.

ee n a y n o . Bo r D : t s i a log h o p n a u t i h m Im Dr. T ee s a r u S Dr. e l l l e c i M Dr.

t e o l a y a t wit a r e e h T Phuong ng Noimua Griffith

The Immune System is the body system that fights off infection and pathogens.

 The immune system is the body system that fight off infection and pathogens. The immune system relies on physical barrier to keep pathogens out.  Your skin is you body’s first line of defense. The skin physically blocks invading pathogens. Many pathogens cannot survive in this kind of environment.

Cells and proteins fight the body’s infections • • •

•

The cells of your immune system spring into action. White blood cell find and kill pathogens that have gotten past the body’s external barriers. When a pathogen enters the body , basophils in the blood stream or mast calls found in other tissue release chemical signals. A phagocyte is a call that destroys pathogens by surrounding and engulfing them. T-lymphocytes and B-lymphocyte , also called T-cells and B-cell. T-cells destroy body cells that are infected with pathogens. B-cells produce proteins that inactivate pathogens that have not yet infected a body cell.

The six main types of white blood cells and their roles in fighting infection are summarized in 1. Basophil 2. Mast cell

-

3. Neutrophil

-

4. Macrophage 5. Lymphocyte 6. Eosinophil

-

- make chemicals that cause inflammation in the bloodstream. make chemicals that cause inflammation in the body tissues. engulfs damaged body cells and foreign invaders ; phagocyte. engulfs damaged body cells and some bacteria ; phagocyte. destroy infected body cells or produces protein that inactivate pathogens. injects poisonous packets into parasites , such as protozoa.

Proteins 1. Complement proteins are made by white blood cells and by certain organs. Some complement proteins weaken a pathogen ’s cell membrane , allowing water to enter the cell and cause it to burst. 2. Antibodies are proteins made by B-cells. Antibodies help the clump, making them easier to engulf and destroy. 3. Interferons are proteins produced by body cells that are infected by a virus. If viruses cannot enter healthy cells , they cannot reproduce. Other interferons stimulate an inflammation reponse.

Immunity prevents a person from getting sick from a pathogen •

•

•

•

•

If you are immune to a pathogen , it mean that you will not get sick when that pathogen invades your body. There are two types of immunity - passive and active. Passive Immunity is immunity that occurs without the body ’s undergoing an immune response. Passive immunity is transferred between mother and child. However , some viruses only made members of a specific species sick. Genetic immunity is immunity that a species has because a pathogen is not specialized to harming that species. Active immunity is immunity that your body produces in response to a specific pathogen that has infected or is sick by a particular pathogen more than once. Sometimes people get the same colds or flus over and over again thought out their lifetime. Each time a different strain of virus invades,your immune system has to start from the beginning again.

31.3 Immune Responses