Defence Against Disease  To understand how the body defends itself against disease Monday, June 06, 2016

Pathogen Barriers  Complete the pathogen barriers worksheet

Pathogen Barriers Wax traps micro- organisms Hairs and mucus stop micro-organisms from entering the body Skin barrier stops micro- organisms from entering the body Tears contain an enzyme which kills micro- organisms Saliva contains an enzyme which kills micro- organisms Blood contains white blood cells which kill any micro-organisms within the body

Antibody and pathogen cards – find your matching partner The antibody will only work if it is connected to this specially shaped site. This design means that the antibody does not harm normal body cells because they do not carry the attachment site. These are the areas (antigens) where the antibody will attach.

White Blood Cells  There are several different types of white blood cells, each with different functions, but they can be put into two main groups: -  Phagocytes or macrophages  Lymphocytes

Phagocytes Destroy Pathogens Digestive enzymes attack the ingested microbe and begin to break it down. The microbe is destroyed. The chemicals that are released from the digested microbe are used in other parts of the cell.

Phagocytes

Lymphocytes  Pathogens contain certain chemicals that are foreign to the body and are called antigens  Each lymphocyte carries a specific type of antibody - a protein that has a chemical 'fit' to a certain antigen  When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen White blood cell Pathogen (coated in antigens) Antibodies attach

Lymphocytes also release antitoxins. Remember that microbes can cause an infected person to feel ill by releasing toxins (poisons). The first way white blood cells defend the body is by releasing antitoxins. These chemicals are designed to neutralise the effects of the toxins and render them harmless. 1. Producing antitoxins

toxins bacterium white blood cell antitoxins Antitoxin links to the toxin and neutralises its effect. The toxin is now harmless. This happens on a large scale and reduces the effects of the infection.

Lymphocytes

Fighting Pathogens  Create a cartoon strip to explain how white blood cells get rid of pathogens and make you immune…  Your cartoon should be about the chicken pox virus and you should try to explain why you become immune to the virus after you first get it

skin Blood vessel Red blood cells White blood cells Pathogen

 White blood cells detect a foreign body and surround it

 White blood cells make antibody against the pathogen. The antibodies also make the pathogens clump together Antibody – this is specific to this particular pathogen

 The antibody acts as a marker for other white blood cells to come along and engulf the pathogen White blood cells that destroy pathogens

 The pathogen has been destroyed and the antibody is left in the blood stream (active immunity)  *In passive immunity the body is actually given the antibodies – this only lasts at most a few years

1. How long did it take to start producing antibodies after the first infection? 2. How long did it take to start producing antibodies after the second infection? 3. Explain why antibodies were produced more quickly after the second infection. 4. Suggest why the person did not become ill after the second infection.

True or False?True or False? 1. Red blood cells defend your body against disease. 2. Antibodies make microorganisms clump together so that they can be engulfed more easily. 3. Antibodies make antitoxins to destroy the toxins made by microorganisms. 4. The immune system protects our bodies against infection. 5. Antigens destroy microorganisms by making them clump together. 6. White blood cells make chemicals called antigens. 7. White blood cells destroy microorganisms in five different ways. 8. Microorganism cells have antigens on their outside. 9. An antigen can only recognise and fight one particular microorganism.