Describe Cell Mediated Immunity

Question 1

Explain T cells and the cell mediated response

Answer 1

T cells encounter their antigen for the first time, they become sensitised to it.

T cells cannot detect free antigen in body fluid.

To recognise and be activated by antigen, the T cells must be presented with it on the membrane of another cell.

These cells are called antigen presenting cells (APCs)

Many different cell types present antigen to T cells, and so are important in activating the adaptive immune system when antigen is present.

Question 2

What are the 4 types of T cells?

Answer 2

1. Cytotoxic : inactivate anything carrying antigens by releasing powerful toxins. Main function is to destroy abnormal body cells which are infected or cancerous.
2. Helper : most common T cell. Essential for cell mediated and antibody mediated immunity. Produce cytokines to support and promote cytotoxic cells and macrophages. Stimulates B cells to produce antibodies.
3. Regulatory : these cells act as ‘brakes’, turning off activated T and B cells. This limits the powerful and potentially damaging effects of the immune response. Regulatory T cells are involved in immunological tolerance. They help prevent the development of antoimmunity and protect the foetus in pregnancy.

Memory : respond rapidly to subsequent encounters with the same antigen.