1. The Immune System Non-Specific Immunity

2. What You Should Know The human body has the capacity to protect itself against pathogens, some toxins and cancer cells through the immune system. Non-specific defences include physical defence as the epithelial cells form a physical barrier and chemical defences – chemicals are produced and secreted against infection. Inflammatory response includes the release of histamine by mast cells causing vasodilation and increased capillary permeability. The increased blood flow and secretion of cytokines leads to an accumulation of phagocytes and the delivery of antimicrobial proteins and clotting elements to the site of infection. Phagocytes and NK (natural killer) cells release cytokines which stimulate the specific immune response. Phagocytes recognise surface antigen molecules on pathogens and destroy them by phagocytosis. NK cells induce the pathogen to produce self-destructive enzymes in apoptosis.

3. The body has an immune system for defence against – pathogens –some toxins produced by living things –cancer cells Immunity is the ability of the body to –resist infection by a pathogen –or to destroy the pathogen if it invades the body Non-specific Cellular Defence

4. First Line Defence-Non Specific Barriers defence –The skin is composed of layers of epithelial cells which provide a physical barrier against bacteria and viruses –Mucus membranes that line the digestive and respiratory tracts are also composed of epithelial cells

5. Chemical defence -Secretions from the skin’s sweat glands and sebaceous glands keep the pH of the skin too low for many organisms -Secretions such as tears and saliva contain lysozyme which digests bacterial cell walls killing them -Cells in mucus membranes secrete mucus which traps microorganisms -Ciliated cells in the trachea sweep mucus and trapped microbes up and away from the lungs –Acid secreted by the epithelial cells lining the stomach destroys many of the microbes which have been swallowed bacteria (yellow) sticking to the mucus (blue) on the hair-like cilia

6. Inflammatory Response Prevents –spread of injurious agents to adjacent tissues –disposes of pathogens and dead tissue cells –promotes tissue repair

7. Mast Cells and Histamine Histamine – –released from mast cells and promotes vasodilation of local arterioles and increased permeability of local capillaries Signs: redness, pain, heat and swelling Increased blood flow and permeability of capillary walls enhances the migration of phagocytes to the damaged area

8. Cytokines Cytokines are cell signalling proteins released by phagocytes and natural killer cells when in contact with a pathogen They are important in both non specific and specific immunity Secreted from white blood cells at the site of injury The increased blood flow and secretion of cytokines leads to o an accumulation of phagocytes which carry out phagocytosis o the delivery of antimicrobial proteins and clotting elements to the site of infection

10. Phagocytes Phagocytes also release cytokines which stimulate the specific immune response by activating lymphocytes Phagocytes recognise surface antigen molecules on the pathogens and destroy them by phagocytosis

11. Natural Killer Cells Natural killer cells also release cytokines which stimulate the specific immune response by activating lymphocytes NK cells attack virus infected and cancerous cells NK cells release proteins that cause the cell to produce self-destructive enzymes resulting in cell death by apoptosis