TMJC Immunity & Infectious Diseases Notes

Page 1 of 50 Tampines Meridian Junior College JC2 H2/9744 Biology 2024 Extension Topic A 14. Immunity and Infectious Diseases SYLLABUS OVERVIEW No. Overarching Idea Topics 1 Core Idea 1 The Cell and Biomolecules of Life Cell – The Basic Unit of Life 2 Biomolecules of Life and Cellular Transport 3 Core Idea 3 Energy and Equilibrium Transformation of Energy – Photosynthesis and Cellular Respiration 4 Core Idea 2 Genetics and Inheritance Genetics and Inheritance (I) – The Cell Cycle 5 Genetics and Inheritance (II) – DNA Replication and Gene Expression 6 Genetics and Inheritance (III) – DNA Mutations and their Consequences 7 Genetics and Inheritance (IV) – Molecular Techniques in DNA Analysis 8 Genetics and Inheritance (V) – Organization of Genome & Control of Gene Expression in Eukaryotes [Includes Core Idea 1D: Stem Cells] 9 Genetics and Inheritance (VI) – Organization and Inheritance of Viral Genomes 10 Genetics and Inheritance (VII) – Organization of Genome & Control of Gene Expression in Prokaryotes 11 Genetics and Inheritance (VIII) - Inheritance 12 Core Idea 3 Energy and Equilibrium Communication and Equilibrium in Multicellular Organisms 13 Core Idea 4 Biological Evolution Biological Evolution 14 Extension Topic A Infectious Diseases Immunity and Infectious Diseases 15 Extension Topic B Impact of Climate Change on Animals & Plants Climate Change – Causes and Impacts on Animals and Plants

Page 2 of 50 TOPIC SYNOPSIS Micro-organisms, e.g. viruses and bacteria, cause diseases which disrupt the equilibrium of physiological systems in humans. This extension topic explores how some infectious diseases are diagnosed and treated. The following question should help you frame your learning: • What cause infectious diseases? • How does the body respond during an infection? • How can infectious diseases be prevented or diagnosed and treated? With an understanding of how the human immune system functions, this concept explores the development of vaccines and vaccines are used to eradicate infectious diseases like smallpox. Yet, not all viruses can be eliminated by vaccines. The influenza virus and HIV infects humans. While treatment is available through vaccines and anti -viral drugs, they are still present in the population due to their high mutation rate. Besides viral infections, diseases can also be caused by bacterial infections. Tuberculosi s is caused by the bacteria Mycobacterium tuberculosis . Although successful vaccination programs in Singapore have kept the infection under control, there have been new cases appearing in the population and it remains a fatal disease in developing countries. LEARNING OUTCOMES Extension Topic A: Infectious Diseases Candidates should be able to: a) Describe the specific (adaptive) immune system, including active, passive, natural-acquired and artificially- acquired immunity, and the non-specific (innate) immune system. b) Outline the roles of B lymphocytes, T lymphocytes, antigen-presenting cells and memory cells in specific primary and secondary immune responses. c) Explain the relationship of the molecular structure of antibodies to their functions, using immunoglobulin G, IgG, as an example. d) Explain how somatic recombination, hyper -mutation and class switching result in millions of different antibody molecules. e) Discuss how vaccination can control disease (e.g. in the eradication of smallpox), limited to vaccination stimulates immunity without causing the disease and vaccination of a high enough proportion of the population can break the disease transmission cycle. f) Discuss the benefits and risks of vaccination. g) Explain how viruses, including influenza virus and HIV, cause diseases in humans through the disruption of host tissue and function (e.g. HIV and helper T cells, influenza virus and epithelial cells of the respiratory tract) h) Explain the mode of transmission and infection of bacterial pathogens, using Mycobacterium tuberculosis as an example. i) Describe the modes of action of antibiotics, including penicillin, on bacteria.

Page 3 of 50 LECTURE OUTLINE 1. Overview of the immune system 2. Innate immunity (non-specific) 2.1 Barrier/physical defense 2.2 Cellular innate defense 2.3 Antimicrobial proteins 2.4 Inflammatory response 3. Adaptive immunity (specific) 3.1 Antigen recognition by B cells and antibodies 3.1.1 Structure of B cell antigen receptor 3.1.2 Structure of antibody e.g. IgG 3.2 Antigen recognition by T cells 3.3 Development of B and T cells 3.3.1 Generation of B cell and T cell diversity 3.3.2 Proliferation of B cells and T cells 3.3.3 Immunological memory 3.4 Role of T cells, B cells, antigen-presenting cells and memory cells in adaptive immunity 3.4.1 Helper T cell activates B cells and cytotoxic T cells 3.4.2 Cytotoxic T cell kills infected cells 3.4.3 B cell secretes antibodies that bind to and mark pathogens for destruction 3.4.4 Summary of the humoral and cell-mediated immune responses 4. Comparison between innate and adaptive immunity 5. Vaccination and disease control 5.1 Types of immunity 5.2 Vaccination and the eradication of smallpox virus 5.3 Benefits and risks of vaccination 6. Infectious diseases caused by viruses 6.1 HIV weakens the immune system by destroying helper T cells 6.2 Influenza virus damages respiratory epithelial cells 7. Infectious diseases caused by bacteria 7.1 Mycobacterium tuberculosis infects the lung and causes tuberculosis 7.2 How antibiotics kill bacteria 7.3 How bacteria gain resistance to antibiotics

Page 4 of 50 1. Overview of the immune system • Pathogens e.g. virus, bacterium, fungus are agents that cause diseases and infect a wide range of animals. • Dedicated immune cells , derived from the hematopoieti c stem cells in the bone marrow (Fig. 1.1), are found in the body fluids and tissues of most animals. These immune cells specifically interact with and destroy pathogens. Additional responses to infection can take many forms, including proteins that create holes in bacterial membranes or block viruses from entering body cells. • These and other defenses make up the immune system, which enables an animal to avoid or limit many infections. Fig. 1.1: All cellular components in the blood, including the immune cells, arise from multipotent hematopoietic stem cells in the bone marrow.

Page 5 of 50 • All animals have innate immunity (details in Section 2), a defense that is activated immediately upon infection and is the same whether or not the pathogen h as been encountered previously. It provides the first line of defense against pathogens (Fig. 1.2a/b). • Adaptive immunity (details in Section 3) is activated after the innate immune system activation and develops more slowly. This immune response is enhanced by previous exposure to the infecting pathogen . It creates an army of immune cells specifically designed to attack a specific pathogen, conferring lifelong protective immunity to reinfection with the same pathogen (Fig. 1.2a and 1.2b). Fig. 1.2a: Overview of animal immunity. Immune responses in animals can be divided into innate and adaptive immunity. Some components of innate immunity contribute to activation of adaptive immune defenses. Fig. 1.2b: Immediate and delayed response by the innate and adaptive immunity, respectively.

Page 6 of 50 2. Innate immunity (nonspecific) Learning outcome: Describe the specific (adaptive) immune system, including active, passive, natural -acquired and artificially - acquired immunity, and the non-specific (innate) immune system. • Innate immunity refers to non-specific defence mechanisms that is activated immediately or within hours of a pathogen’s appearance in the body. These mechanisms include physical barriers such