Cell mediated response

Where do T-cells mature?

In the thymus

The cell mediated response is the response involving…

T-cells and body cells

What are Antigen presenting cells?

Any cell that presents a non-self antigen on their surface.

Why is the cell-mediated response considered specific?

Because T-cells respond to antigens on the surface of cells

Describe 4 kinds of Antigen-presenting cells

• Infected body cells (present viral antigens on surface)

• A macrophage which has engulfed and destroyed a pathogen

• Cells of a transplanted organ (different shaped antigens compared to your own)

• Cancer cells (abnormal shaped)

Why are T-cell responses described as cell-mediated?

Because T-cells only respond to antigens which are presented on cells and not antigens detached from cells and in bodily fluids (e.g. the blood)

What occurs first in the cell mediated response?

• Once a pathogen has been engulfed and destroyed by a phagocyte

• The antigens are positioned on the cell surface (it’s now called an antigen presenting cell)

Which immune system response occurs BEFORE the cell-mediated response?

Phagocytosis

What occurs after the antigens are positioned on the cell surface?

The receptors on the surface of Helper T-cells attach to the antigens on Antigen Presenting Cells.

What occurs once the Helper T-cell’s receptors attach to the antigens on APC?

• The Helper-T cells are activated

• It divides by mitosis and makes large numbers of clones

What occurs once the helper T-cells have divided by mitosis?

The cloned helper T-cells differentiate into different cells.

What is the function of cells that cloned helper T-cells differentiate into?

• Some remain as helper T-cells which can activate B-lymphocytes

• Some stimulate macrophages to perform more phagocytosis

• Some become memory cells for that antigen

• Some become cytotoxic T-cells

Function of cytotoxic T-cells?

Destroying abnormal or infected cells

How do cytotoxic T-cells carry out their function?

• They release a protein called perforin

• This embeds in the cell surface membrane and makes a pore so that any substances can enter or leave the cell

• Leading to cell death.

Which kind of infections are cytotoxic t-cells most used in and why?

• Viral infections

• Because viruses infect body cells

Why are some normal body cells sacrificed when cytotoxic t-cells perform their function?

In order to prevent viral replication

Why do we get a sore throat when we have a cold?

• The cytotoxic T cells are destroying infected body cells in the throat