the immune system

immunology

• the stufy of the immune system

immune system

• integrated system of cells and molecules that defend against disease, reacts against infectious pathogens

what occurs when the immune system works against us?

• allergy, autoimmune diseases and grafft rejections

innate immunity

• broad specificity

• no memory

• rapid response

• leucocytes include phagocytes, NK cells

• soluble factors: lysozymes, complement and interferons

leucocytes

• derived from pluripotent stem cells in the bone marrow, givivng rise to myeloid and lymphoid cells

keratinized skin (innate simmunity)

• outer layer of skin (also in hair and nails), when the barrier is disrupted, this lead to infections

secretions (innate immunity)

• sebum, fatty acids and lysozymes (destroys the walls of gram-positive bacteria)

mucus (innate immunity)

• cilia traps microbes

low pH (innate immunity)

• stomach acid cells

commensals (innate immunity)

friendly bacteria, when using antibiotics these are also killed

phagocytes

• white blood cells that engulf and digest pathogens. first person to see these was Elie Metchnikoff in starfish 1883

neutrophils

• the main type of phagocyte whichare short lived and fast moving, lysosomes releases enzymes and/or hydrogen peroxide

• contains a green pigment

mononuclear phagocytes

• 2 types: in blood (monocytes) and tissues (macrophages)

• monocytes replenishes macrophages

• they differ in shape and are long lived

natural killer (NK) cells

• kills virally infected host cells non-specifcally

• important in self/non-self recognition and may kill cancer cells

• to tell if a cell is infected/cancerous, they will kill the targets unless they recognise self-proteins (MHC)

complement system

• ~20 proteins in blood, activated on infection which can do bacterial cell lysis on gram-negative cells

defensins

• made by neutrophils, inserted in the membrane of bacterial cells which disrupts it

interferons

• produced by virally infected cells, protect uninfected cells by binding to them and can activate macrophages and natural killer cells

cytokines

• small, secreted proteins that bind to cells or change gene expression like interleukins

inflammatory mediators

• brought about by histamines and prostaglandins

inflammation

• swelling is caused by the increased capillary permeability

• pain is due to damaged nerve endings

• redness is caused by the dilation of blood vessels

• phagocytes migrate into the tissues due to inflammation

temperature response

• acts on the hypothalamus

• reduces levels of iron in blood

• stimulates phagocytosis