Introduction to the immune system

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• Immunity: Resistance to diseases Immune system: Cells, tissues and mediators Coordinated Reactions: Immune response

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• Defence against infections Recognise and respond to foreign proteins Defence against tumours Antibodies are highly specific reagents for detecting any class of antigens

1. Implications

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   • Without immune system, it increases susceptibility to infections, vaccination boosts immune defence Barrier to transplantation and gene therapy Immune evasion, immunotherapy Immunological approach for lab used in clinical and research 

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• Hypersensitivity/T cell mediatd diseases

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• Innate Immunity vs Adaptive immunity

1. Innate immunity

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   • Dendritic Cell Mast Cell Macrophage Natural Killer cell Complement Proteins Granulocytes
   1. Flowchart

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      • Toll-like receptors leads to production of cytokines: ROS (reactive oxygen species) and it leads to killing to microbes The N-formyl methionyl receptors allows increase in adhesion of blood/microbes and it aids in migration into tissues Mannose receptors increases phagocytosis of microbes to phagosome and leads to killing of microbes.
      1. Outcomes
         1. Possible Defects

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            • Congenital defects (i.e immunity defects) Acquired defects: like irradiation and chemotherapy Evasion by Microbes: Resistance to phagocytosis and the immune system
2. Adaptive Immunity

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   • B Cells (generate antibodies) T Cells and the daughter T cells.
   1. Flowchart

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      • 2 possible scenarios: Humoral immunity or cell mediated immunity THe antigen can react with B lymphocytes or macrophages and hence it produces reaction within the B lymphocyte to "memorize" and to secrete antibodies The T-helper cell, makes memory and help to kill cells.
   2. Properties

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      • Specific receptor/co receptor expression Generation of cells with long life span due to ability to 'clone' Selective proliferation and differentaition of antigen specific lymphocytes Elimination of self reactive cells by clonal detection : Tolerance.
   3. B-Cells

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      • Recognise through Anitbody binding, to eliminate extracellular pathogens. It then activate the cell to divide and release more antibody antibody then cirulates to bind to surface of bugs then it alerts/primes the organism is foreign and it allows the complement to bind and destroy cell and block pathogen and neutralize toxins.
   4. T-Cells

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      • It phagocytosed microbes in macrophages intracellular microbes replicate within the cells and the T-cells recognise small parts on the surface of HOST cells
      1. CD8

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         • Peptides on MHC class 1 Peptides from inside cells Kill cells
      2. CD4

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         • Peptides on MHC class II Peptides from outside Leads to help.
3. Mechanisms

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   • As time passes, the innate immunity will switch to adaptive immunity and back and forth if needed.
4. Comparison

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   • Specificity: Innate has class shared by class of microbes, not that specific Adaptive immunity recognise specific microbial antigens or nonmicrobial antigens Receptors: Innate immunty, react to receptors encoded in the germline Adaptive: Encoded by genes, highly sophisticated Distribution: Innate immunity: Nonclonal Adaptive immunity: Clonal