Introductions to the immune systems.pptx

introduction to immune system

1. Welcome to the Immune System: A Defence for Life The immune system is a complex network of cells, tissues, and organs that protect the body from disease. It's crucial for fighting infections and maintaining overall health.

2. What is the Immune System? Body's Defence The immune system is a complex network of cells, tissues, and organs that protect the body from harmful pathogens, such as bacteria, viruses, and parasites. Immune Response It recognises and eliminates these invaders through a series of coordinated responses, keeping us healthy and fighting off diseases. Disease Prevention The immune system is crucial for preventing infections and maintaining overall health.

3. Organs of the Immune System Bone Marrow The bone marrow is the site of production for all types of blood cells, including immune cells. Thymus Gland The thymus gland plays a crucial role in the development and maturation of T lymphocytes, critical for adaptive immunity. Lymph Nodes Lymph nodes act as checkpoints, filtering lymph fluid and housing immune cells that detect and respond to pathogens. Spleen The spleen filters blood, removing old and damaged red blood cells and housing immune cells, contributing to both innate and adaptive immunity.

4. Immune Cells and Their Roles White Blood Cells These are the primary cells of the immune system, responsible for defending against pathogens. Macrophages These large cells engulf and destroy pathogens, acting as scavengers and antigen presenters. T Cells They are critical for cell-mediated immunity, recognising and destroying infected cells. B Cells B cells produce antibodies, which bind to and neutralise pathogens.

5. Bone Marrow: Manufacturing Hub Bone marrow is a spongy tissue found within the bones, particularly in the pelvis, ribs, and sternum. It's the primary site of haematopoiesis, the process of creating all the different blood cells, including red blood cells, white blood cells, and platelets. Haematopoietic stem cells (HSCs) reside in the bone marrow, acting as precursors for all blood cells. They are capable of self-renewal and differentiation into different cell types. The bone marrow's role in producing immune cells makes it crucial for a healthy immune system.

6. Thymus Gland: T Cell Training Ground The thymus gland is a vital organ in the immune system. It plays a crucial role in the development and maturation of T cells, key players in the adaptive immune response.

7. Lymph Nodes: Checkpoints for Immunity Lymph nodes are small, bean-shaped organs scattered throughout the body. They act as filtering stations for the lymphatic fluid, which carries immune cells and other substances. When pathogens enter the lymph nodes, immune cells, such as lymphocytes, macrophages, and dendritic cells, are activated to fight the infection. Lymph nodes swell during infection as immune cells proliferate to combat the threat.

8. Spleen: Filtering the Blood Spleen Structure The spleen is a fist-sized organ, located in the upper left abdomen. It is surrounded by a capsule, which encloses the splenic parenchyma, the functional tissue of the spleen. Blood Filtration The spleen filters the blood, removing old and damaged red blood cells, platelets, and white blood cells, and preventing these cells from circulating in the bloodstream. Immune Response It plays a crucial role in the immune system by storing white blood cells and mounting an immune response to foreign substances like bacteria and viruses.

9. Innate Immunity: First Line of Defence Rapid Response Innate immunity acts as a first responder, immediately tackling threats. Non-Specific This arm of the immune system targets a broad range of pathogens. No Memory The innate immune response doesn't remember previous encounters with pathogens.

10. Adaptive Immunity: The Second Line of Defence Innate Immunity Immediate, non-specific response. It's the body's first line of defence against pathogens. Recognises common features of pathogens. It reacts quickly, but has no memory of past encounters. Adaptive Immunity Slower, but specific. It adapts to recognise and target particular pathogens. Learns from previous encounters, providing long-lasting immunity. It involves T and B cells.

11. Antigens: Triggers for Immune Response Foreign Substances Antigens are molecules that trigger an immune response. They are usually foreign substances, such as bacteria, viruses, or toxins. Specific Recognition Immune cells have receptors that recognise and bind to specific antigens, leading to the activation of an immune response. Immune Activation The binding of an antigen to its receptor triggers a cascade of events, leading to the activation of various immune cells and the production of antibodies.

12. Antigen Presentation: Alerting the Immune System 1 Antigen Capture Antigen-presenting cells (APCs) engulf antigens, like bacteria or viruses. 2 Processing APCs break down the antigen into smaller fragments, preparing them for display. 3 Presentation APCs display antigen fragments on their surface, using MHC molecules.

13. T Cells: Coordinators of Immunity Types of T Cells Helper T cells (TH) Cytotoxic T cells (TC) Regulatory T cells (Treg) Roles of T Cells T cells are crucial for coordinating and regulating the immune response to foreign invaders. They recognise and target specific antigens, triggering the destruction of infected cells and promoting the production of antibodies by B cells.

14. B Cells: Antibody Producers Antibody Factories B cells are responsible for producing antibodies, which are proteins that specifically target and neutralise pathogens. Antigen Recognition Each B cell has a unique antibody receptor on its surface, enabling it to bind to a specific antigen. Plasma Cells Upon activation by antigen, B cells differentiate into plasma cells, which are highly specialised antibody-producing factories. Memory B Cells Some activated B cells become memory cells, providing long-term immunity to specific pathogens.

15. Natural Killer Cells: Eliminating Infected Cells 1 1. Cytotoxic Lymphocytes Natural killer (NK) cells are a type of cytotoxic lymphocyte, crucial for eliminating cells infected with viruses or bacteria. 2 2. Immune Surveillance NK cells constantly patrol the body, searching for cells with abnormal surface markers, indicating infection or malignancy. 3 3. Direct Cell Killing Upon encountering a target, NK cells release cytotoxic granules, triggering apoptosis (programmed cell death) in the infected cell. 4 4. Bridge Between Innate and Adaptive NK cells play a crucial role in linking the innate and adaptive immune responses, contributing to overall immune protection.

16. Inflammation: Sign of Immune Activation Redness Caused by increased blood flow to the area. Swelling Due to fluid accumulation in the tissues. Pain Triggered by chemical mediators released by immune cells. Heat Also caused by increased blood flow.

17. Fever: The Body's Natural Defence Elevated Body Temperature Fever is a natural immune response where the body raises its core temperature. Inhibiting Pathogen Growth Elevated temperature slows down or even stops the growth of pathogens. Enhancing Immune Response Fever accelerates the immune system's response and improves the function of immune cells.

18. Phagocytes: Engulfing Pathogens 1 1. Identifying Targets Phagocytes use receptors on their surface to recognise and bind to pathogens. 2 2. Engulfing and Internalising The phagocyte's membrane surrounds and engulfs the pathogen, forming a vesicle called a phagosome. 3 3. Destroying the Pathogen The phagosome fuses with lysosomes, which contain enzymes that break down the pathogen.

19. Complement System: Biochemical Cascade Protein Cascade The complement system involves a series of proteins that interact in a cascade-like manner. Activation Pathways There are three main activation pathways: classical, alternative, and lectin, each triggered by different stimuli. Membrane Attack Complex (MAC) The complement system culminates in the formation of the MAC, which disrupts the cell membrane of pathogens.

20. Cytokines: Chemical Messengers of Immunity Communication Network Cytokines are small proteins that act as messengers within the immune system. They are released by various immune cells and regulate immune responses. They coordinate the activities of different immune cells, ensuring a coordinated response to pathogens and inflammation. Types of Cytokines Various types of cytokines exist, each with specific functions. Interleukins (ILs) Interferons (IFNs) Tumour Necrosis Factors (TNFs) Chemokines

21. Antigen-Antibody Interactions Antigen-antibody interactions are crucial for the adaptive immune response, where antibodies specifically bind to antigens, initiating the immune response. This binding is highly specific, enabling the immune system to target and neutralize specific pathogens or toxins. 1 Binding Antibodies bind to specific epitopes on antigens. 2 Neutralisation Antibodies block the pathogen's ability to infect cells. 3 Opsonisation Antibodies enhance phagocytosis by immune cells. 4 Complement Activation Antibodies trigger the complement system, leading to pathogen lysis.

22. Major Histocompatibility Complex (MHC) MHC Class I Found on all nucleated cells, presenting antigens to cytotoxic T cells. MHC Class II Present on antigen-presenting cells, displaying antigens to helper T cells.

23. Clonal Selection and Expansion Antigen Encounter An antigen binds to a specific receptor on a naive lymphocyte. Lymphocyte Activation This binding activates the lymphocyte, triggering a cascade of events. Clonal Expansion The activated lymphocyte undergoes rapid proliferation, creating a clone of identical cells. Differentiation Some clones differentiate into effector cells, while others become memory cells.

24. Memory Cells: Long-Term Protection Immune Memory Memory cells provide long-lasting protection from previously encountered pathogens. Rapid Response Upon re-exposure, memory cells quickly activate and mount a targeted immune response. Enhanced Protection This rapid response helps to prevent or reduce the severity of future infections.

25. Vaccines: Priming the Immune System Introducing Antigens Vaccines introduce weakened or inactive versions of pathogens, called antigens, into the body. These antigens mimic a real infection, triggering an immune response without causing illness. Generating Memory Cells The immune system learns to recognise and fight specific antigens. This results in the creation of memory cells, which provide long-term protection against future infections.

26. Vaccine Types and Mechanisms Live-Attenuated Vaccines Weakened versions of the virus or bacteria are used. They replicate weakly, stimulating an immune response without causing disease. Inactivated Vaccines The virus or bacteria is killed but retains its antigens. These vaccines trigger an immune response without the risk of infection. Subunit Vaccines Only specific parts of the pathogen, such as proteins or carbohydrates, are used to induce an immune response. mRNA Vaccines Introduce genetic material that instructs the body to produce viral proteins, triggering an immune response without using live virus.

27. Herd Immunity: Protecting the Community Collective Protection Herd immunity occurs when a large proportion of a population is immune to a disease. Reduced Transmission This significantly reduces the spread of the disease, protecting those who are vulnerable. Vaccination Importance Vaccination is the most effective way to achieve herd immunity. Public Health Benefit Herd immunity protects those who cannot be vaccinated due to medical reasons.

28. Autoimmunity: When the Immune System Turns on Itself Misdirected Attack In autoimmune diseases, the immune system mistakenly targets the body's own cells and tissues as foreign invaders. This leads to chronic inflammation, tissue damage, and a range of symptoms that vary depending on the specific disease. Examples Rheumatoid arthritis: affects the joints Type 1 diabetes: destroys insulin-producing cells Multiple sclerosis: attacks the central nervous system

29. Immune Deficiencies: Challenges to Immunity Compromised Defence Immune deficiencies occur when the immune system is weakened, leaving the body vulnerable to infections. Types of Deficiencies These can be primary, caused by genetic factors, or secondary, resulting from conditions like HIV or malnutrition. Impact on Health Individuals with immune deficiencies are at increased risk of frequent and severe infections, requiring special medical care. Treatment Options Treatment can involve therapies like immunoglobulin replacement, bone marrow transplants, or antiviral medications.

30. Recap and Key Takeaways Immune System The immune system protects the body from pathogens and diseases. Cells & Organs Immune cells and organs work together to defend the body. Innate & Adaptive Immunity Innate immunity provides immediate defence, while adaptive immunity adapts to specific threats. Vaccines Vaccines prime the immune system for long-term protection against specific diseases.