MB 502: Immunology Unit 3 PDF

MB 502: Basics of Immunology UNIT 3 DEFENSE MECHANISM AND IMMUNIZATION Presented by Vaibhavi G. Mandanka M. Sc Microbiology, GET,GATE(life Science) Arts,Science and Commerce college KHOLWAD, Kamrej, Surat. ...

MB 502: Basics of Immunology UNIT 3 DEFENSE MECHANISM AND IMMUNIZATION Presented by Vaibhavi G. Mandanka M. Sc Microbiology, GET,GATE(life Science) Arts,Science and Commerce college KHOLWAD, Kamrej, Surat.  Content Overview and ImportanceLearning Outcomes 3.1 Innate Defense Mechanism 3.1.1 Phagocytosis 3.1.2 Inflammation 3.2 Adaptive defense: Antibodies 3.2.1 Antibody detailed structure 3.2.2 Types of Antibodies 3.2.3 Antibody functions 3.3 Monoclonal Antibodies and its production 3.3.1 Hybridomas 3.3.2 Hybridoma production 3.3.3 Clinical Application 3.4 Vaccines 3.4.1 Principles of vaccination  Overview & Importance ❑ Immune System: Protects the body from harmful invaders (like bacteria/viruses). ❑ Innate vs. Adaptive: 1. Innate Immunity: Quick, general response. 2. Adaptive Immunity: Slow, targeted, remembers invaders. ❑ Inflammation & Phagocytosis 1. Inflammation: White blood cells, proteins, and fluid rush to infection/injury sites to fight invaders. 2. Phagocytosis: Immune cells eat invaders, then alert the body to boost the immune response. ❑ Antibodies & Vaccines 1. Antibodies: Proteins that mark invaders for destruction. 2. Monoclonal Antibodies: Lab-made, target specific invaders, key in advanced treatments. ❑ Vaccines: Train the immune system to fight specific invaders, crucial post-COVID.  Learning Outcomes 1. Understand basic mechanisms of pathogen removal. 2. Explore practical methods in antibody production. 3. Grasp the structure and function of antibodies. 4. Highlight the role of immunology in public health, focusing on vaccine strategies.  Innate Défense Mechanism Purpose: Protects organisms from harmful dangers through quick, built-in responses. Immunization: Intentional development of immune responses to fight off pathogens. Innate Immunity: First line of defense, present from birth, providing rapid, non-specific protection.  Physical Barriers: Skin, mucous membranes block pathogen entry. Chemical Defenses: Antimicrobial peptides, enzymes prevent pathogen growth. Cellular Defenses: Macrophages, neutrophils, natural killer cells identify, engulf, and destroy pathogens. Role: Initiates immune response, promotes inflammation, and activates adaptive immunity.  Phagocytosis Definition: Phagocytosis (from Greek: "phagein" = to eat, "cyte" = cell) is a process where cells engulf and digest solid particles like pathogens or debris. Role in Immunity: A key part of the innate immune response, helping cells like macrophages and neutrophils capture and destroy harmful substances.  ❑ Process: 1. Engulfment: Phagocytes engulf the target particle. 2. Phagosome Formation: The particle is enclosed in a membrane-bound compartment (phagosome). 3. Digestion: Phagosome fuses with lysosomes, where enzymes break down the ingested material. Importance: Vital for both innate and adaptive immune responses, helping protect against infections and maintain tissue health.  Phagocytosis vs Auto-phagocytosis 1. Extracellular Pathogen: Phagocytosis - Engulfment of external pathogens. 2. Intracellular Pathogen: Autophagy - Degradation of internal pathogens.  Phagocytosis Steps 1. Chemotaxis & Recognition: Chemotaxis: Phagocytic cells (neutrophils, macrophages) are drawn to infection sites by chemical signals from damaged tissues and pathogens. Recognition: Phagocytic cells have receptors called PRRs (Pattern Recognition Receptors) that detect PAMPs (Pathogen-Associated Molecular Patterns) on pathogens.  2. Recognition Mechanisms: Opsonin-Independent (Non-Opsonic): Direct receptor-based recognition. Opsonin-Dependent (Opsonic): Uses complement proteins to tag pathogens for recognition.  3. Pattern Recognition Receptors (PRRs): Several membrane-bound PRRs on the phagocyte surface detect unique patterns on pathogens. Signal Transduction: Once bound, PRRs can facilitate enzymatic activation of cytokines or transduce signals to a common transcription activation pathway, upregulating cytokine expression.  Example: Mannose Receptor One multi-lectin PRR is the mannose receptor, found on dendritic cells and macrophages. It recognizes and binds the repeating mannose, fucose, or N- acetylglucosamine components of various microorganisms, including Mycobacterium tuberculosis, Pneumocystis carinii, Candida albicans, and the capsular polysaccharides of Streptococcus pneumoniae and Klebsiella pneumoniae.  ❑ NOD-Like Receptors (NLRs) and Toll-Like Receptors (TLRs) 1. NOD-Like Receptors (NLRs): A type of PRR that is soluble and found in the phagocyte’s cytoplasm. Function: Monitors internal signals and controls programmed cell death (apoptosis). NOD Receptors: Around 22 similar proteins in humans, they detect signals from various pathogens (viruses, bacteria, fungi) and send these signals to the host cell nucleus to trigger gene expression and an appropriate immune response. 2. Toll-Like Receptors (TLRs): TLR-4: Detects lipopolysaccharides and heat shock proteins in bacteria. TLR-9: Recognizes the CpG dinucleotide pattern in DNA from dying bacteria. TLR-2: Alerts the immune system to bacterial lipoproteins and peptidoglycans.  ❑ Attachment, Engulfment & Phagosome Formation 1. Pseudopodia Extension: The phagocytic cell extends pseudopodia (cytoplasmic extensions) toward the pathogen or particle. 2. Phagocytic Cup Formation: Pseudopodia surround the pathogen, enclosing it in a phagocytic cup. 3. Phagosome Formation: The phagocytic cup seals off, forming a vesicle called a phagosome that contains the engulfed particle.  ❑ Autophagy Process 1. Ubiquitin Labeling: Intracellular microbes or their products are tagged with ubiquitin, similar to how proteasomes recycle proteins. 2. Phagophore Formation: Ubiquitin "labels" bacteria for capture by a phagophore (free-floating, open membrane). The phagophore surrounds the bacteria, forming a double membrane autophagosome, initiating the process of autophagocytosis or autophagy.  ❑ Fusion with Lysosome 1. Phagosome-Lysosome Fusion: The phagosome fuses with a lysosome, an organelle filled with digestive enzymes, forming a phagolysosome. In the phagolysosome, the phagosome's contents mix with lysosomal enzymes. 2. Key Enzymes in Lysosome: 1. Lysozyme 2. Phospholipase A2 3. Ribonuclease 4. Deoxyribonuclease 5. Proteases are among the enzymes that degrade the contents. 3. Reactive Nitrogen Species (RNS): Macrophages, neutrophils, and mast cells generate RNS, such as Nitric Oxide (NO) and its derivatives (Nitrite, Nitrate), enhancing enzyme activity. RNS are highly cytotoxic, helping to kill trapped bacteria.  ❑ Digestion Breakdown in Phagolysosome: 1. Enzymes within the phagolysosome break down the engulfed particles, including pathogens, cellular debris, or foreign materials. 2. Release of Breakdown Products 3. Nutrients and other breakdown products are released into the cytoplasm of the phagocytic cell.  ❑ Microbial Killing & Elimination Acidic Environment: Lysosomal enzymes create an acidic environment within the phagolysosome, aiding in particle degradation.  Reactive Oxygen Species (ROS): 1. Includes 2. Superoxide Radicals (O₂⁻), 3. Hydrogen Peroxide (H₂O₂), 4. Singlet Oxygen (¹O₂), and 5. Hydroxyl Radicals (OH⁻). ROS enhance the killing of pathogens.  Reactive Nitrogen Species (RNS): 1. Includes 2. Nitric Oxide (NO), 3. Nitrite (NO₂⁻), and 4. Nitrate (NO₃⁻). RNS can block cellular respiration by interacting with iron in electron transport proteins.  ❑ Elimination: After digestion, the remnants and waste materials are transported to the cell's surface in vesicles.  ❑ Exocytosis: Vesicles fuse with the cell membrane, releasing waste outside the cell. Macrophages and Dendritic Cells become antigen-presenting cells: 1. Microbial fragments are transported to the endoplasmic reticulum. 2. Peptides combine with histocompatibility proteins and are delivered to the cell membrane.  Inflammation ❑ What is Inflammation? It’s the body's natural process of responding to harmful agents like physical injuries, chemicals, or infections by microbes.  ❑ Types of Inflammation 1.Acute Inflammation Duration: Short-term, happens quickly. Cause: The body's initial response to an infection or injury. Main Players: Primarily involves neutrophils (a type of white blood cell). Outcome: Once the harmful agent (like a microbe) is removed by the immune system, inflammation decreases, and the body begins to repair the affected area. 2. Chronic Inflammation Duration: Long-term, can last for months or even years. Cause: Occurs when the harmful agent persists, such as in ongoing infections or certain diseases. Main Players: Involves lymphocytes, macrophages, and plasma cells (all types of immune cells). Outcome: The inflammation continues as the body tries to manage the persistent issue, which can lead to ongoing tissue damage if not resolved.  Acute Inflammation ❑ What is Acute Inflammation? It’s the body’s initial, quick reaction to harmful stimuli like injury or infection. ❖ Key Features of Acute Inflammation 1.Symptoms: Redness: Due to increased blood flow to the area. Heat: The inflamed area becomes warm. Swelling: Caused by fluid buildup. Pain: Due to pressure from swelling and release of certain chemicals. Loss of Function: In some cases, the affected area may not function properly. 2. Role of Immune Cells: Neutrophils and Macrophages: These immune cells rush to the site of injury or infection to eliminate harmful agents and clean up damaged cells. 3. How Immune Cells Recognize Harmful Agents: ✓ Pattern Recognition Receptors (PRRs): These receptors on immune cells detect specific patterns on pathogens. ✓ Response Triggered: Once PRRs bind to these patterns, they trigger the release of pro- inflammatory cytokines (small signaling proteins like interleukins and TNF). ✓ Purpose of Cytokines: These cytokines help coordinate the immune response, making sure the body effectively fights off the infection or repairs the damage.  Inflammatory Response to Tissue Injury 1. Tissue Injury: When tissue is injured (due to trauma, infection, etc.), the body starts an inflammatory response to protect, repair, and fight off threats. 2. Release of Chemokines: Chemokines: Signaling molecules released at the injury site. Role: Activate nearby capillaries and call immune cells to the injury. 3. Activation of Capillaries: Chemokines cause nearby capillaries to increase blood flow and make their walls more permeable. 4. Selectin Expression: Activated Capillaries: Endothelial cells in the capillaries express selectins (adhesive molecules) on their surfaces. Purpose: Selectins help recruit immune cells to the injury site. 5. Attraction of Neutrophils: Neutrophils: A type of white blood cell, one of the first responders to the injury. Attraction: Selectins draw neutrophils to the injury site. 6. Neutrophil Activation: Chemokines Activates neutrophils, preparing them for their immune response role. 7. Activation of Integrins on Neutrophils: Integrins: Adhesive molecules that help neutrophils stick to endothelial cells. Outcome: Neutrophils adhere to the capillary walls. 8. Extravasation and Attack: Extravasation: Neutrophils move through the capillary walls to reach the injury site. Role: They eliminate pathogens and promote tissue repair through processes like phagocytosis. 9. Chemotaxis and Immune Cell Recruitment: Initial chemokines attract not just neutrophils but other immune cells, working together to fight off threats and repair tissue. 10. Acidity and Chemical Mediators: Local Acidity: Tissue damage and immune activity increase acidity, activating enzymes and pathways in inflammation. 11. Activation of Kallikrein and Bradykinin Release: 1. Kallikrein: An enzyme activated by increased acidity. 2. Bradykinin Release: Kallikrein triggers bradykinin, which affects capillary cells and mast cells. 12. Effect on Capillary Cells and Mast Cells: ✓ Bradykinin: Causes vasodilation (widening of blood vessels) and activates mast cells. 13. Vasodilation and Mast Cell Degranulation: Outcome: Increased blood flow and capillary permeability, leading to swelling and redness. Mast cells release histamine. 14. Histamine Release and Effects: Histamine: Enhances swelling and redness, part of the body’s defense. 15. Cytokines and Blood Vessels: Cytokines: Cause blood vessels to dilate, increasing blood flow (redness and heat) and permeability (swelling). 16. Substance P and Nerve Damage: Nerve Damage: Damaged nerves release substance P, Which binds to mast cells, enhancing the inflammatory response and pain. 17. Activation of Prostaglandins: ✓ Prostaglandins: Lipid molecules involved in inflammation, activated by bradykinin. 18. Increased Swelling and Pain Sensitization: ✓ Prostaglandins: Increase swelling by promoting vasodilation and making capillaries more permeable. They also make nerve endings more sensitive, increasing pain.  Neutralizing and Eliminating Pathogens During Acute Inflammation 1. Purpose of Acute Inflammation: The body launches a strong response to neutralize and eliminate pathogens, containing the threat and promoting tissue repair. 2. Increased Blood Flow and Capillary Dilation: Response to Pathogens: Blood vessels near the infection site dilate, increasing blood flow. Benefit: More immune cells, oxygen, and nutrients are delivered to fight off the infection. 3. Antimicrobial Factors and Leukocyte Influx: Leukocytes: Immune cells like neutrophils and macrophages arrive at the site. Action: They release antimicrobial factors and engage in phagocytosis (engulfing and destroying pathogens). 4. Release of Antimicrobial Factors: These factors help destroy the pathogens and support the overall immune response. 5. Blood Leakage and Temperature Increase: Capillary Permeability: Increased permeability allows blood to leak into tissue spaces. Result: The area becomes warmer, creating an environment less favorable for microbes and boosting the immune response. 6. Fibrin Clot Formation: Clot Formation: A fibrin clot may form in the inflamed area. Purpose: Acts as a barrier to prevent the spread of pathogens to other parts of the body. 7. Phagocyte Recruitment and Pathogen Engulfment: Phagocytes: Neutrophils and macrophages are attracted to the site. Action: They recognize pathogens, engulf them, and break them down through phagocytosis. 8. Chemical Signaling and Bone Marrow Stimulation: Chemical Signals: Released at the inflammation site, they stimulate bone marrow. Result: Increased production and release of neutrophils and other immune cells into the bloodstream, enhancing the immune response. 9. Objective of the Inflammatory Response: 1. Combined Efforts: 2. Increased blood flow, 3. antimicrobial factors, 4. leukocyte action, and 5. the inflammatory environment work together to create an inhospitable setting for pathogens. Goal: Eliminate the threat, prevent its spread, and promote tissue repair and recovery.  Chronic Inflammation ❖ What is Chronic Inflammation? Chronic inflammation occurs when inflammation persists even after the initial trigger (like infection or injury) is resolved. ❖ Potential Consequences: Prolonged inflammation can lead to tissue damage and contribute to various diseases. ❖ Associated Conditions: Chronic inflammation is often linked to serious health issues, including: 1. Cardiovascular Disease 2. Diabetes 3. Certain Autoimmune Disorders ❖ Molecular Understanding: Research into the molecular mechanisms of inflammation has improved our understanding and treatment of these conditions. ❖ Immunomodulatory Therapies: Targeted Treatment: Drugs that specifically target inflammatory molecules, such as cytokines, have been developed to manage chronic inflammatory diseases. Example: These therapies can help control inflammation and reduce the risk of related complications.