Lesson 1 Barriers: Immune System and Defence PDF

LESSON 1 Barriers OBJECTIVES: LESSON 1 Name the three key functions of the immune system Describe key pathogens causing disease and routes of transmission Describe layers of immune defence First line of defence Second line of defence INNATE IMMUNITY VS ADAPTIVE IMMUNITY...

LESSON 1 Barriers OBJECTIVES: LESSON 1 Name the three key functions of the immune system Describe key pathogens causing disease and routes of transmission Describe layers of immune defence First line of defence Second line of defence INNATE IMMUNITY VS ADAPTIVE IMMUNITY Third line of defence First and second line of defence Compare and contrast  PROBLEM-BASED LEARNING – CASE STUDY Case scenario Bronwyn (38) cut her finger. The next day, the skin around the cut had become red and warm. She has come to the pharmacy to seek advice. How can I tell if a wound is infected? What are signs of infection and inflammation What can you tell the patient about the skin as an immune barrier and the inflammatory response?  KEY FUNCTIONS OF THE IMMUNE SYSTEM Immune defense Immune homeostasis Immune surveillance  Functions Normal Abnormal  Disease Immune Clearance of infection Hypersensitivity Defense Immunodeficiency Immune Homeostasis Eliminate injured/senile cells Accumulation of cell debris/dysfunctional cells (degenerative diseases) Tolerance of self components Autoimmune IMMUNE DEFENCE The immune system protects the body from pathogens that cause disease. The immune system has a series of defences. The immune system includes three lines of defence against foreign invaders: physical and chemical barriers, nonspecific resistance, and specific resistance. The first line of defence are the physical and chemical barriers, which are considered functions of innate immunity. The second line of defence is nonspecific resistance, which also is considered a function of innate immunity. The third line of defence is specific resistance, which is considered a function of acquired immunity. PATHOGENS  INFECTION AND TRANSMISSION OF PATHOGENS 1. Infection via droplets or particles in the air 2. Contact infection and smear infection 3. Infection via blood and tissue 4. Infection via contaminated water and food LAYERS OF IMMUNE New defens DEFENCE es that our bodies learn (adapti ve) After exposur Specialist eImmune to cells microor (cellular) – blood, lymph, ganisms tissue specifi (humoral) Soluble components Things that permeatec our body (blood, respons lymph) e Barriers Skin Mucous THE FIRST LINE OF INNATE DEFENCE Different types of barriers that keep most pathogens out of the body. Regardless of the type of pathogen, however, the first line of defence is always the same. Mechanical barriers Skin (tough, difficult for pathogens to penetrate) Mucous membranes (secrete mucus that traps pathogens, hair-like cilia that remove pathogens) Sneeze or cough (removes pathogens from nose or throat or upper airways) Tears (wash pathogens from the eyes) THE FIRST LINE OF INNATE DEFENCE Different types of barriers that keep most pathogens out of the body. Regardless of the type of pathogen, however, the first line of defence is always the same. Chemical barriers Body openings or inner body linings Sweat, mucus, tears, saliva contain enzymes that kill pathogens Urine is too acidic for many pathogens Stomach acid kills pathogens that enter the GI tract with food or drink  THE FIRST LINE OF DEFENCE – MOLECULAR RESPONSE Molecular barriers Complement system in the blood: blood proteins/ proteolytic cascade leading to opsonisation (phagocytosis) or formation of a lytic pore on cells. PAMP-PAR Pattern recognition receptors (PRRs) on most innate immune cell recognize conserved molecular patterns common to various microbes (PAMPs – pathogen-associated molecular patterns) Lysozymes in tears, nasal secretions, saliva, gastric secretions:  lytic enzyme that attacks the protective cell walls of bacteria. Interferons(IFN):  signalling proteins made and released by host cells in response to the presence of several pathogens, such as viruses, bacteria, parasites, and also tumour cells. C-reactive protein (CRP) in the blood: binds to lysophosphatidylcholine expressed on the surface of dead or dying cells (and some types THE FIRST LINE OF INNATE DEFENCE Different types of barriers that keep most pathogens out of the body. Regardless of the type of pathogen, however, the first line of defence is always the same. Biological barriers Organisms that help protect the body Harmless bacteria on skin or in GI tract Microbiome The skin microbiome: a healthy bacterial balance  THE SECOND LINE OF DEFENCE A Pathogen enters the body: what next? The inflammatory response First reaction to the body to tissue damage or infection Triggered by chemical mediators: cytokines, histamines Chemical mediators communicate with other cells and coordinate the inflammatory response Symptoms at the site of infection/wound: red, warm, swollen The inflammatory response is discussed here  Note: Phagocytosis THE SECOND LINE OF and cell motility lesson in PH1123 DEFENCE Leukocytes The chemicals that trigger the inflammatory response attract leukocytes to the site of injury or infection. Leukocytes are white blood cells. Their role is to fight infections and get rid of debris. Leukocytes may respond with either a nonspecific or a specific defence. A nonspecific defence is the same no matter what type of pathogen is involved. An example of a nonspecific defence is phagocytosis. This is the process in which leukocytes engulf and break down pathogens and debris. Leukocytes involved in the third line of defence are described in lesson 3 Phagocytes in immunity LESSON SUMMARY Barriers that keep out pathogens are the body’s first line of defence. They include mechanical, chemical, and biological barriers. The second line of defence attacks pathogens that manage to enter the body. It includes the inflammatory response and phagocytosis by nonspecific leukocytes.  TRANSLATION TO DISEASE AND PRACTISE - EXAMPLE First aid is an essential life skill, especially for healthcare professionals who have regular contact with people in the local community. How should I wash wounds? Wash minor cuts and grazes to remove any dirt by rinsing them under gently running water or using alcohol-free wipes. Pat the wound dry with a gauze swab or clean non-fluffy cloth, then cover with an adhesive plaster or dressing. If there is a risk that the wound could be infected, advice patient to see his/her GP or practice nurse. Wounds that are bleeding heavily shouldn’t be washed, as this will wash away all the clotting agents (Put pressure on the wound (e.g. with a hand, t-shirt or tea towel) to stop or stem the flow of blood until help arrives, call ambulance) NICE guidance https://www.nice.org.uk/guidance/conditions-and-diseases/infections  PROBLEM-BASED LEARNING – APPLY CONCEPT Case scenario Bronwyn (38) cut her finger. The next day, the skin around the cut had become red and warm. She has come to the pharmacy to seek advice. How can I tell if a wound is infected? Explain to the patient that a wound is at risk of infection if: it's been contaminated with dirt, pus or other bodily fluids there was something in the wound before it was cleaned, such as gravel or a shard of glass it has a jagged edge  PROBLEM-BASED LEARNING – APPLY CONCEPT Case scenario Educe the patient that signs a wound Bronwyn (38) cut her finger. The next day, the has become infected include: skin around the cut had become red and warm. She has come to the pharmacy to seek advice. swelling, redness and increasing pain in the affected area pus forming in or around the wound feeling generally unwell a high temperature (fever) of 38C or above swollen glands under your chin or in your neck, armpits or groin Explain how the inflammatory response helps fight an infection Advice that: a bacteria-infected wound can usually be successfully treated with a short course of antibiotics.