Core Concepts in Immunology

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 site3. The mast cells secrete factors that mediate vasodilation and vascular constriction4. Blood, plasma and cells increase delivery to wound5. Neutrophils secrete factors that kill and degrade pathogens 6. Neutrophils and macrophage kill pathogens by phagocytosis7. Macrophage secrete cytokines8. Cytokines attract immune cells to the wound site and activate immune cells involved in repair9. The inflammatory response continues until the pathogen is destroyed and the wound is repaired

Cytokines are involved in Identification and Discrimination in the Immune ResponseNote: IL - Interleukin and TNF - Tumor Necrosis FactorCytokines IL – 6 stimulates B cell activityCytokine IL – 12 promotes T cell activityCytokine IL – 8 attracts neutrophilsCytokine  IL – 1 and TNFα stimulate the inflammatory response

Identification and Discrimination in the Immune Response