Antigens and the Immune system

Why are lymphocytes able to distinguish between pathogens and self cells?

Because each type of cell has specific molecules, usually proteins, on its surface that identify it

Which four different types of surface molecules enable lymphocytes to identify non-self cells?

1) Pathogens (eg. bacteria)

2) Cells from other organisms of the same species (eg. organ transplant)

3) Abnormal body cells (eg. cancer cells)

4) Toxins (pathogens release them into the blood)

When are lymphocytes made in humans?

When they are a foetus

What kind of cells are we most likely going to be exposed to as a foetus?

Self-cells

Why do the lymphocytes complementary to the antigens on self-cells die or become suppressed?

To prevent the lymphocytes from attacking our own cells

Which lymphocytes are remained in our body?

Lymphocytes that are complementary to pathogenic and non-self cells

Where does the lymphocyte suppressing antigens of the self cell occur after birth?

In the bone marrow

What causes the symptoms of autoimmune disease?

Lymphocytes that attack self-cells are produced

Define an antigen

A cell-surface molecule which stimulates an immune response

1) How can the shape of an antigen change?

2) What is this known as?

• Through a mutation occuring in the gene which codes for the antigen in the pathogen DNA

• Antigen variability

Why is any previous immunity to the pathogen no longer effective when the antigen’s shape has changed?

Because all the memory cells in the blood will have a memory of the old antigen shape