Unit 4 – Immunology and Public Health
To learn about the immune system and non-specific cellular defences
By the end of the lesson I should be able to
• Give examples of physical (e.g epithelial cells) and chemical (e.g secretions, stomach acid) defences against infection.
• Describe the inflammatory response to include release of histamine by mast cells, causing - vasodilation
- Increased capillary permeability• State that this response results in increased blood flow.• State that the resulting secretion of cytokines leads to an accumulation of phagocytes
and the delivery of anti-microbial proteins and clotting elements.• Describe the function of phagocytes to include the release of cytokines, stimulation of
the specific immune response and recognition of surface antigens, leading to phagocytosis.
• Describe the process of apoptosis by NK cells to include the release of cytokines, stimulation of the specific immune response and the induction of viral infected cells to produce self-destructive enzymes.
• Immunity is the ability of the body to – resist infection by a pathogen – or to destroy the pathogen if it invades the body
• The body has an immune system for defence against– pathogens, – some toxins produced by living things– cancer cells
Non-specific Cellular Defence
Epithelial cells are our first line of defence against infection.
They line the surfaces and cavities of the entire body.
Form a physical barrier against infection.
These cells cover almost the entire surface of the body.
They grow constantly upwards and outwards from the bottom layer and by around 14 days they have become dead cells called stratum corneum which flake off taking any bacteria or pathogens with them.
Epithelial cells also produce secretions such as enzymes, hormones and lubricating fluids that can defend against infection.
SecretionsOn all the inside surfaces of the body that can be exposed to bacteria and pathogens a substance called mucus traps dirt and germs, preventing them from entering the blood. Various glands produce antimicrobial secretions that help kill microbes.
• Tiny hairs at the entrance to the nose.
• Cough and sneeze reflexes.
• ‘Friendly’ bacteria.
Think – pair - share
• Under what circumstances might this first line of defence fail?
• What might happen if bacteria manage to cross the barrier?
• As a class try to come up with as many answers as possible
• (may include cuts to the skin – breaking the barrier, use of antibiotics – killing off ‘helpful’ bacteria, over-cleanliness, immune-compromised individuals etc). If bacteria cross the barrier this could lead to infection and further immune responses.
• Prevents – spread of injurious agents to adjacent tissues,– disposes of pathogens and dead tissue cells,– promotes tissue repair
Chilblains – inflammation of the toes (or other extremities) caused by prolonged exposure to moisture and cold.
Acne – inflammation of the skin caused by bacteria in the pores
Inflammation is a common response to bee/wasp stings
Tonsilitis – inflammation of the tonsils
Mast cells are present in most tissues surrounding blood vessels and nerves, and are especially prominent near the boundaries between the outside world and the inside of our bodies, such as the skin, mucous in the lungs and digestive tract, as well as the mouth, conjunctiva, and nose.
They contain histamine and cytokines which cause the typical inflammatory response.
Non-specific inflammationThe inflammatory response is triggered when something breaks the skin.
Cytokines attract white blood cells called phagocytes to the area and the release of antimicrobial proteins or clotting elements to the damaged area.
Histamines are also released which cause the capillary to vasodilate and become more permeable.
Copy and complete the table FunctionMast cell
Once the bacterium is inside the phagocyte, lysosomes fuse with the vesicle, digesting the bacterium.VIDEO
Phagocytes are cells which will engulf and digest a foreign particle such as bacteria.They recognise the foreign antigen molecules on its surface then bind with the bacterium and engulf it by endocytosis.
Natural killer cellsNatural killer (NK) cells are found in the blood and are constantly looking for signs of an infection. They can also release cytokines but they have an important role in destroying a pathogen-infected cell.They look for a cell which has not got the normal surface antigens or self antigens and knows that it must be infected. It then destroys it with self-destructive enzymes perforating the plasma membrane, bursting it, a process called apoptosis.
Physical and chemical defences Epithelial cells
Inflammatory response Mast cells- histaminehistamine and cytokinescytokines
Non-specific cellular responses
NK cells- apoptosis cytokinescytokines
For indiscriminate killing of pathogens
Phagocytes and natural killer cells Members of the notorious white blood cell gang
Comic strip• Students will work with their shoulder partner to create a short comic strip
telling the story of how their white blood cell ended up on a wanted poster.
• The story must be biologically correct. Students must use class resources to help them.
• You have 25 minutes to come up with a storyline and produce a brief outline of your comic.
• Choose either– Phagocytes – NK
Questions1. Name a secretion made by the epithelial cells lining the
inside of the body.2. What name is given to the immediate response of the
body to a cut?3. What are mast cells?4. Why do the capillaries vasodilate?5. What general name do we give disease-causing
organisms?6. Describe what an antigen is made of and where it is
found.7. What is the name of the cell signalling molecule
produced by many immune cells?
Questions8. Describe the process of phagocytosis.9. What are NK cells?10.Describe the stages involved in apoptosis.
Task – Create a Glossary table for the below words including their definitions
Epithelial cellsInflammatory responsePathogenAntigenNon-selfMast cellsHistaminesCytokinesVasodilation PermeabilityPhagocytesLysosomesNatural killer cellsApoptosis