Core Concepts in Immunology

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Identification

The detection of foreign microbes from foreign 'self' antigens is an important regulatory mechanism the immune system employs. The immune system needs to be able to distinguish self from non self, and harmful from self.

There are specific receptors on immune cells and foreign microbe cells that enable identification and discrimination of foreign microbes from foreign 'self' antigens.

The immune system has evolved early at multicellularisation. It has evolved mechanisms to identify and discriminate different antigens present to the immune cells. This immune system has evolved from genes.

Discrimination

There are specfic molecules of the surfaces of cells that helps the immune system to distinguish non self from self. It is necessary mechanism the immune system uses to regulation identification and discrimination.

The immune system identifies microbes through activation in signalling pathways. For example, Toll Like receptors act as microbial detectors/receptors on the surfaces of cells.

The mechanism of discrimination of self from non self is a specific response in the adative immune response.

Example of discrimination pathway against microbes by a signalling pathway:

The lipopolysaccharide on the surface of a bacterium is identified by

a TLR bound to a dendritic cell (TLR4); this TLR signals to intracellular

components to bind and activate NFkB; NFkB activates nuclear cytokines which

send a signal to cytokines outside the cell activating a series of pathways.

Example of an Identification Pathway:

1. Bacteria and other pathogens enter a wound

2. The platelets from blood release

blood clotting proteins at the wound site

3. The

mast cells secrete factors that mediate vasodilation and vascular

constriction

4. Blood, plasma and cells

increase delivery to wound

5. Neutrophils

secrete factors that kill and degrade pathogens

6. Neutrophils and macrophage kill pathogens by phagocytosis

7. Macrophage secrete cytokines

8. Cytokines attract immune cells to the

wound site and activate immune cells involved in repair

9. The inflammatory response continues until

the pathogen is destroyed and the wound is repaired

Cytokines are involved in Identification and Discrimination in the Immune Response

Note: IL - Interleukin and TNF - Tumor Necrosis Factor

Cytokines IL – 6

stimulates B cell activity

Cytokine IL – 12

promotes T cell activity

Cytokine IL – 8 attracts neutrophils

Cytokine IL – 1 and TNFα

stimulate the inflammatory response

Identification and Discrimination in the Immune Response