Defensive Strategies -2 Immune System Part 1 PDF

DEFENSIVE STRATEGIES -2 Immune System Part 1 (Dr Tom Kelly) Dr Neil Coughlan  IMMUNE SYSTEM -1 ◼ Evolution linked to endosymbiosis ◼ Eukaryotes, multi-celled organisms, animals ◼ A vital system ◼ Highly complex ◼ Understanding of system has led to real benefits...

DEFENSIVE STRATEGIES -2 Immune System Part 1 (Dr Tom Kelly) Dr Neil Coughlan  IMMUNE SYSTEM -1 ◼ Evolution linked to endosymbiosis ◼ Eukaryotes, multi-celled organisms, animals ◼ A vital system ◼ Highly complex ◼ Understanding of system has led to real benefits for mankind e.g. vaccines ◼ Campbell 12th Edition ◼ Chapter 47:Animal Defences Against Infection. Concepts 47.1, 47.2, 47.3 GENERAL INTRODUCTION 1 ◼ External defences ◼ Innate Immune system ◼ The Adaptive, or as it is also known, the Acquired Immune Response ◼ The Inflammatory Response ◼ Cells and soluble factors (e.g. secreted by cells) GENERAL INTRODUCTION 2 ◼ PRIMARY FUNCTION OF THE IMMUNE RESPONSE IS TO FIND AND DESTROY INVADING INFECTIOUS AGENTS e.g. VIRUSES, BACTERIA, PROTISTANS (=PROTISTA or PROTOZOA), WORMS etc. ◼ AND REDUCE TO A MINIMUM THE DAMAGE THEY CAUSE An immune system response involves: ◼ A) Recognizing the invader and ◼ B) “mounting a reaction against it to eliminate it” (Roitt et al., 1998)  INFECTIOUS AGENTS-1 ◼ MOSTLY MICROBES SUCH AS VIRUSES AND BACTERIA ◼ BUT ALSO WORMS ◼ FLEAS, LICE AND TICKS (which vector many microparasites) ◼ ALL CAN CAUSE DAMAGE TO THE HOST, AND SOME CAN AND DO KILL ◼ VIRUSES INCLUDE INFLUENZA, HIV, COVID-19, MEASLES AND MUMPS  INFECTIOUS AGENTS-2 ◼ BACTERIA INCLUDE TYPHOID, CHOLERA, MRSA, E.coli, BUBONIC PLAGUE, LYME DISEASE ◼ PROTOZOA INCLUDE MALARIA, SLEEPING SICKNESS, RED WATER FEVER ◼ WORMS INCLUDE LIVER FLUKE, TAPEWORMS AND ROUNDWORMS  INFECTIOUS AGENTS-3 ◼ ALL VIRUSES AND MANY BACTERIA AND PROTOZOA ONLY REPLICATE INSIDE CELLS : i.e. are intracellular parasites or pathogens. “Cell is a safe place to be, if you are a pathogen” – plasma membrane impenetrable to soluble factors: e.g. antibodies ◼ So, for the immune system to confront and eliminate these infectious agents, it must RECOGNIZE AND DESTROY THESE INFECTED CELLS - i.e. collateral damage.  INFECTIOUS AGENTS-4 ◼ But other bacteria, some protozoa and larger parasites like worms live in extracellular spaces, body fluids and tissues. ◼ So a different type of immune response is necessary to deal with these: https://www.youtube.com/watch?v=6uDH1LmV ztI&ab_channel=AnimatedbiologyWitharpan ◼ Intracellular pathogens have to leave cell to infect another and have to move through blood and tissue fluid so confronted by same immune response as above  DEFENSIVE STRATEGIES-2 IMMUNE-1 EXTERNAL DEFENSES AND THE INNATE IMMUNE RESPONSE  This Lecture ◼ Exterior aka External defences ◼ Inflammatory Response ◼ Innate Immune Response ◼ Cells, and Soluble factors ◼ Opsonisation ◼ Phagocytes and Phagocytosis ◼ Myeloid line; Antigen Presentation; APCs; Macrophage-Monocyte system  EXTERNAL DEFENSES-1 ◼ MOST IMPORTANT FIRST LINE OF DEFENSE ◼ SKIN IMPENETRABLE BARRIER TO PATHOGENS ◼ VERY TIGHT GAP JUNCTIONS BETWEEN CELLS ◼ FATTY ACIDS AND FLORA =HARMLESS BACTERIA COMPETE WITH POTENTIAL INVADERS =MICROBIOME –also VIP in GUT “Symbiotic bacteria” MICROBIOME- VERY IMPORTANT  INFLAMMATORY RESPONSE-1 ◼ PATHOGENS CAUSE INFLAMMATION Three components: ◼ Increased blood supply to the infected area ◼ Increased permeability of capillaries –allowing escape of larger molecules and cells ◼ Migration of leukocytes (i.e., white blood cells) out of venules into surrounding tissues ◼ Leukocytes: mostly neutrophils but later monocytes and lymphocytes  INNATE IMMUNITY-1 ◼ Natural or native immunity ◼ In place before infection occurs ◼ Its “poised” and ready for rapid response (Abbas and Lichtman 2005) ◼ Physical barriers, cellular and soluble factors ◼ Reacts to infectious agents (e.g., microbes) ◼ NON SPECIFIC AND WITHOUT A MEMORY INNATE IMMUNITY-2 CELLS ◼ MYELOID LINE ◼ CELLS ARE PHAGOCYTES ◼ POLYMORHONUCLEAR GRANULOCYTES Include: -Neutrophils, Eosinophils -Mast cells and Basophils (allergic response) -Monocytes, macrophages, dendritic cells (all antigen presenting cells =APC): breakdown and present the infectious agent to Adaptative Response. -Antigen-presenting cells are involved in both the innate and adaptive immune responses. Macrophages have key role for APC Pluripotent hematopoietic stem cells differentiate into bone marrow as myeloid or lymphoid stem cells Mature in the Thymus Gland INNATE IMMUNITY-SOLUBLE FACTORS ◼ PROTEINS AND PEPTIDES ◼ COMPLEMENT 30 PROTEINS ◼ LYTIC, OPSONINS, CHEMOTACTIC ◼ INTERFERONS ◼ PROTECT CELLS AGAINST INVASION BY VIRUSES ◼ OTHER PROTEINS INCLUDE CYTOKINES AND CHEMOKINES Play an important role in limiting the spread of certain virus infections  INNATE IMMUNITY OPSONISATION ◼ An opsonin is a “macromolecule that becomes attached to the surface of a microbe and can be recognised by surface receptors of neutrophils and macrophages and increases the efficiency of phagocytosis” ◼ Opsonisation “the process of attaching opsonins such as igg or complement fragments, to microbial surfaces to target the microbes for phagocytosis” Abbas and Lichtman (2005) “cellular and molecular immunology”, Elsevier. PHAGOCYTOSIS – Amoeba type cell PHAGOCYTE Dendritic cells (DCs) represent a heterogeneous family of immune cells that link innate and adaptive immunity. “The immune system consists of A) The Innate Immune Response, and B) The Adaptive Immune Response. The Innate Immune Response is something you are born with. It only reacts to microbes, but it is non-specific and it does not have a memory. Therefore, its potency or strength does not increase with repeated exposure to the pathogen. Adaptive Immune Response, sometimes called the Acquired Immune Response, has to develop in response to an invading pathogen. It is highly specific and it has a memory. Its potency or strength increases with repeated exposure to the pathogen.“ T.C. Kelly, November 2021.