Overview of Immunology PDF

Overview of immunolog y Alexander.strachan@plymout h.ac.uk Learning objectives This session is intended to provide a broad overview of immunology for the BDS and DTH programmes. By the end of this session, students should be able to: Describe the primary function of the immune system Describ...

Overview of immunolog y Alexander.strachan@plymout h.ac.uk Learning objectives This session is intended to provide a broad overview of immunology for the BDS and DTH programmes. By the end of this session, students should be able to: Describe the primary function of the immune system Describe the key features of the innate immune system Describe the key features of the adaptive immune system  Suggested resources British Society for Immunology: What is immunology? Khan Academy: Phagocytes Types of immune respons e How to get the most from this session: Take notes and log any words or concepts that are not familiar to review after the session. Refer to recommended resources. You are invited and welcomed to ask questions throughout. I will invite you to think about questions and take part in discussions. I will wait at the end of the session and you are very welcome to come and ask questions or queries. Why is it important for dental professionals to understand how the immune system works? Infectious diseases “Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi; the diseases can be spread, directly or indirectly, from one person to another” World Health Organisation. Can you think of any infectious diseases? Infection is the largest cause of illness worldwide, and one of the highest contributors to global mortality Immune system diseases Disorders of the immune system are common causes of morbidity and mortality. Can you think of any immune system disorders? Why do we have an immune system and what does it do? The major role of the immune system is to protect us from infection with pathogens. What different types of pathogen does the immune system have to us protect against? 1 minute activity 1 minute brainstorm What different types of pathogen does the immune system have to us protect against? What is the main difference between how bacteria and viruses cause disease? How do bacteria multiply compared to viruses? In relation to host cells, where do viruses need to be to cause disease? Is the same true for bacteria? Mechanic immun defenc al Anyeothers??es Immune cells The cellular component of our immune system are the white blood cells (leukocytes). Think about what functions immune cells need to carry out: Recognise infection by microbes Eliminate microbes and clear up damaged cells Remember previous infections  Organ ofth immun syste s e e m Many immune cells collect in the lymphoid organs and All blood wait to be cells are alerted to an made in the infection. bone marrow Some will circulate around the body seeking The immune system is specially designed to recognise “self” and “non-self” Why is this important? Microbial cells have structures that are only present in microbes, and that we never see in the human body. We refer to a structure which activates an immune response as an ANTIGEN. Are there other antigens that you can think of? How does the immune system protect us from pathogens? Cellular and soluble defences Soluble defences are immune defence mechanisms which are carried out by things floating in the blood Cellular defences are immune defence mechanisms which are carried out by cells directly interacting with each other Most immune responses will use a bit of both, but dependant on the infecting organism it will be mostly one or the other. Soluble factors in the immune system Humoral = of the blood Mostly needed for defence against infectious microbes that live OUTSIDE of cells, in the blood. E.g. bacteria, fungi, and parasites. They tend to be too big to fit inside of cells.  Cellular factors in the immune system Let’s consider an infection with bacteria… Abbas, Lichtman, and Pillai. Cellular and Molecular Immunology, 7 th edition. Copyright © 201C2opbyryighSta©u2n0d11ebrysS,aau ndeirms, apnriimnptriontfoEf ElslsevvieireIrncI. nc. What mechanisms does the immune system have to protect against bacteria? Bacteria outside of cells need to be picked up, destroyed and disposed of. The immune system has a number of processes to do this: Phagocytosis: Specialist cells engulf bacteria and break them down in special compartments containing enzymes and toxic free radicals Opsonisation: Helps phagocytic cells to pick up the bacteria Neutralisation: Stops bacteria from binding and colonising the tissue  Phagocyt es:materia and degrad Inges foreig it t n Phage:l to eat Cyte: cell e MΦ NΦ DC Mon o EΦ  Phagocyto sis Cells that have phagocytised pathogens send signals to recruit more immune  Opsonisati on Opsonins Antibodie s Complement* C-reactive protein Prepares pathogen for phagocytosis * More about complement in a minute Neutralisation Neutralisation Complement (abridged) Antibodies Neutralisation, opsonisation, and agglutination Microbe Antibody Microbe + Antibody YY Y Y Y Y Inflammation Dealing with viruses What mechanisms does the immune system have to protect against viruses? Viruses are only on the outside of cells for a short time. In this case, they can be picked up, destroyed and disposed of in a similar way to bacteria. But viruses spend most of their time on the inside of cells where they can replicate. Which of the following mechanisms will be effective against viruses once they are inside? Phagocytosis: Specialist cells engulf bacteria and break them down in special compartments containing enzymes and toxic free radicals Opsonisation: Helps phagocytic cells to pick up the bacteria Neutralisation: Stops bacteria from binding and colonising the tissue Inflammation: Recruits other cells to the site of infection to help Specialist cells are designed to kill other cells infected with viruses Specialist cells can kill infected cells by two mechanisms: 1. Cell to cell contact: Interactions between molecules on the surface of the killer cells and the infected cells cause the infected cell to die by programmed cell death 2. Soluble signals: Killer cells release granules called perforin and granzyme that punch holes in the infected cell membrane and cause programmed cell death. Antigens and immune responses It is energetically expensive to launch an immune response, and because it is deigned to kill microbes, can be toxic to us too. It is very important that we can tell the difference between a microbe and our own tissues. Antibodies, complement proteins, and immune cells - along with many other cell types - can recognise antigens from microbes. Other cell types will signal to the immune cells for help if they recognise an antigen. Antigens are very specific, and are recognised by a precisely matching antigen receptor or antibody. Each time a specific antigen activates an immune response, matching cells which are capable of doing so will “remember” that antigen, so it can quickly eliminate it from the body. This is the basis of how vaccination works.  Vaccination Edward Jenner, 1749 – 1823 Principle: to mimic natural infection without causing disease, and Low level antibody High level antibody induce a memory response to production in response to production in response to protect against future infection Immune defences in the Saliva: oral cavity E.g. Antibodies, Lysozyme, Lactoferrin Gingival crevicular fluid Cytokines, complement, antibodies Lymphoid tissues MALT, tonsils Summary It is vital for dental professionals to understand how the immune system works because it is involved in almost all pathological processes, but especially infectious diseases, immune dysfunctions, and some pharmacology. Different microbes cause disease in different ways, so we need to have an immune response to deal with each type Most bacterial infections are dealt with by: Phagocytosis, opsonisation (complement and antibodies), agglutination, and neutralisation. Most viral infections are dealt with by: Killer (NK and T) cells and anti-viral proteins The immune system is made up of primary organs (bone marrow and thymus), secondary organs (lymph nodes, spleen, lymphoid tissues), cellular (leukocytes) and soluble (antibodies, complement, messenger molecules, and anti-viral proteins) factors. There are two main divisions of the immune system; innate and adaptive. Both work together to protect against pathogens. The oral tissues have a complex and unique immune system… tbc [email protected]  Inflammation Damaged tissues and danger signal activate pain receptors  Inflammation Pathogens, particularly bacteria, tend to like a similar temperature to us (around 37 oC).  Inflammation Blood vessels become leaky to allow more immune cells through to the site of infection  Inflammation Lots of new immune cells collect at the site of infection  Inflammation Pain and swelling make it difficult to use the affected area