Cellular Defense in animals

• skin
• mucus and cilia
• coughing, sneezing, and vomiting
• acid in the stomach
• ear wax
• blood clotting

White blood cells

They recognise and respond to the presence of invading foreign particles

Phagocytosis is the process by which foreign bodies, such as bacteria, are engulfed and destroyed.

phagocytes

• A phagocyte detects chemicals released by a bacterium and moves along a concentration gradient towards it
• The phagocyte attaches to the bacterium and engulfs it in a vacuole
• Lysosomes move towards and fuse with the vacoule and release their powerful digestive enzymes into it
• The bacterium is digested and the breakdown products are absorbed by the phagocyte

In the phagocyte's cytoplasm

• When a person is infected with a virus their body produces antibodies, this is called the primary response.
• The primary response is often unable to prevent the person becoming ill

• If the person recovers and is re-exposed to the same antigen this results in the secondary response
• This time the disease is usually prevented because:
• anitbody production is more rapid
• the concentraion of antibodies produces reaches a higher level
• the higher concentration of antibodies is maintained for a longer time

memory

Lymphocytes are white blood cells which produce antibodies

specific

antigen

Y shaped

A receptor site

The person is exposed to the disease-causing antigen, suffers the disease, makes antibodies and continues to be able to for a long time (or even permanently) after recovery. The person is therefore immune to future attacks by that antigen

The person recieves a small amount of vaccine containing antigens which have been treated in a certain way so that they induce antibody formation but do not cause the disease

Instead of the individuals making antibodies in response to the antigen, ready made antibodies are passed into his/her body.

When antibodies cross the placenta from mother to foetus and from milk to suckling baby.

By extracting antibodies that have been made by one organism (eg horse) and injecting them into another (eg human).

When the T lymphocytes of the recipient's immune system reagard the new tissue as a collection of foreign antigens and attempt to destroy them

identical

Immunosppressor drugs

They greatly inhibit the recipient's immune system and make the person more susceptible to disease