Disease and Immunity


The risk of developing Coronary Heart Disease is increased by:

  • A diet in high saturated or salt
  • Smoking, lack of exercise and excessive alcohol intake, which can damage the heart and the blood vessels

The risk of developing cancer is increased by:

  • Smoking
  • Excessive exposure to sunlight
  • Excessive alcohol intake

A pathogen is an organism that causes disease.

Pathogens enter the body through:

  • Gas-exchange system: pathogens are breathed in and trapped in the mucus that lines the lung epithelium. These cells have cilia that beat and move the mucus up the trachea to the mouth where is it swallowed.
  • The Skin: pathogens on the surface of the skin can enter the bloodstream through cuts. The blood clots and dries to form a scab to prevent this.
  • Digestive system: when you eat or drink food that contains pathogens. Most of these will die in the acidic conditions of the stomach, however some can survive and pass into the intestines. Here they can invade cells of the gut wall and cause disease.

How do pathogens cause disease?

1. Production of TOXINS: harmful molecules

2. DAMAGE to HOST CELLS: rupturing them to release nutrients inside them, breaking down the nutrients for their own use which starves and kills the cell, replicating inside the cells and bursting them when they're released

Antigens are proteins found on the cell surface of pathogens, they bind to antibodies.

The immune system is activated by 'foreign' antigens that are on the pathogens that enter the body.

Stages of the immune response:

  • Phagocytosis
  • T-Cells
  • B-Cells


1. Phagocyte recognises antigen on pathogen surface

2. Phagocyte engulfs pathogen

3. Pathogen is contrained in a phagosome

4. Lysosome fuses with the phagosome and the lysosomal enzymes it contains break down the pathogen

5. The phagocyte presents the pathogen's antigens on its cell surface to activate other immune system cells

T Cell Activation

A T cell is another type of white blood cell. It has proteins on its surface that bind to the antigens presented to it by phagocytes. When these bind…


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