Non-specific responses act in the same way against any pathogen. They are fast, working within minutes to hours, but do not produce memory. They include barriers, inflammation, lysozyme, interferon, phagocytosis and fever (phagocytosis and fever have their own lessons).Barriers: the skin has a tough outer layer of dead, keratinised cells, mucus in the airways traps pathogens, and stomach acid kills most microorganisms that are swallowed.Inflammation: when tissue is damaged or infected, mast cells release histamine and other chemicals. Histamine causes:
• vasodilation of arterioles, increasing blood flow, so the area becomes red and hot
• increased permeability of capillaries, so plasma, phagocytes and antibodies leave the blood and enter the tissue, causing swelling.
Chemicals released at the site also attract phagocytes.Lysozyme: an enzyme found in tears, saliva, mucus and sweat. It hydrolyses the peptidoglycan in bacterial cell walls, especially in Gram positive bacteria, so the bacteria burst by osmotic lysis.Interferon: cells infected by viruses release interferons, proteins that diffuse to neighbouring cells. Interferons make these cells produce proteins that inhibit viral replication, for example by stopping viral protein synthesis, so the virus spreads more slowly. Interferons also activate other immune cells.Together these responses slow an infection while the slower, specific immune response develops.
• vasodilation of arterioles, increasing blood flow, so the area becomes red and hot
• increased permeability of capillaries, so plasma, phagocytes and antibodies leave the blood and enter the tissue, causing swelling.
Chemicals released at the site also attract phagocytes.Lysozyme: an enzyme found in tears, saliva, mucus and sweat. It hydrolyses the peptidoglycan in bacterial cell walls, especially in Gram positive bacteria, so the bacteria burst by osmotic lysis.Interferon: cells infected by viruses release interferons, proteins that diffuse to neighbouring cells. Interferons make these cells produce proteins that inhibit viral replication, for example by stopping viral protein synthesis, so the virus spreads more slowly. Interferons also activate other immune cells.Together these responses slow an infection while the slower, specific immune response develops.