Lecture 1( Introduction to immunology).pptx
- 1. ZERA INTERNATIONAL COLLEGE OF HEALTH SCIENCES DEPARTMENT OF CLINICAL MEDICINE IMMUNOLOGY LECTURE 1: INTRODUCTION TO IMMUNOLOGY Mrs Natasha N Ng’andwe BSc, BMS
- 2. Lecture Outline Define immunity Functions of the immune system Concepts in immunology Unique characteristics of immune responses Comparison between innate & acquired immunity Briefly look at cells of the immune system
- 3. Introduction The term immunity, derived from the Latin “immunis” (exempt), was adopted to designate this naturally acquired protection against diseases such as measles or smallpox. Immunology can be described as a branch of biology that covers the study of immune systems in organisms The emergence of immunology as a discipline was closely tied to the development of microbiology. The work of Pasteur, Koch, Metchnikoff, and many other pioneers of the golden age of microbiology resulted in the rapid identification of new infectious agents, closely followed by the discovery that infectious diseases could be prevented by exposure to killed or attenuated organisms, or to compounds extracted from the infectious agents.
- 4. Functions of the immune system Prevent or limit invasion by microorganisms. Eliminate micro-organisms in the body. Maintain homeostasis both external & internal body environment
- 5. General concepts in immunology 1. Innate (non specific) & acquired (specific) immunity. Innate immunity (non specific) are defenses that we are born with or are present from the time we are bone. Acquired immunity ( specific) are defenses that are induced during the life of the individual as part of the complex sequence of events designated as the immune response.
- 6. HOST RESPONSE TO MICROBIAL WORLD
- 7. LINES OF DEFENSE FIRST LINE : ANATOMICAL BARRIERS Mechanical barriers (skin & mucous membranes) Chemical barriers (acid and antibacterial peptides) Physiological barriers (temperature, pH) SECOND LINE : innate immune cells Phagocytes (monocytes/macrophages, neutrophils and dendritic cells) Natural killer cells (NKCs) Inflammatory cells (mast cells, basophils, eosinophils)
- 8. LINES OF DEFENSE THIRD LINE: adaptive immune cells Lymphocytes (T cells and B cells) Humoral immunity: Immunoglobulins (antibodies) Cell-mediated immunity: T cells
- 9. Unique Characteristics of the Immune Response 1. Specificity For example, immunization with poliovirus only protects against poliomyelitis, not against the flu. The specificity of the immune response is due to the existence of exquisitely discriminative antigen receptors on lymphocytes 2. Memory The ability to remember previous responses and to react more quickly and more intensely. meaning that repeated exposures to a given antigen elicit progressively more intense specific responses.
- 10. Stages of immune response 3 stages- induction, amplification and effector. Induction involves recognition of antigen by specific receptors on lymphocytes .followed by activation of the cells. Amplification –cytokines mediate interaction between cells leading to proliferation and differentiation of T and B lymphocytes. Effector- elimination of pathogens by antibodies, cytotoxic T cells or macrophages.
- 11. Innate immunity Exists prior to invasion (natural immunity). Non-specific, No memory Intact skin and mucous membranes acts as physical barrier to invasion by microorganisms. Chemical properties such as gastric acid. Antibacterial substances found in secretions e.g lysozyme
- 12. Innate immunity Phagocytic cells Include neutrophils, macrophages, dendritic cells, natural killer cells. They Ingest and neutralize microorganisms by exposing them to proteolytic enzymes, lipases, hydrogen peroxide etc. They also act as antigen presenting cells to T lymphocytes bridging innate and acquired immunity.
- 13. Acquired immunity Involves 2 types ; 1. Humoral immunity: Involves the production of antibodies in circulation that eliminate infectious agent Mechanisms antibodies use include Neutralization/blocking, ADCC, Opsonization, Complement fixation 2. Cell-mediated immunity: T cells activate macrophages to kill phagocytosed microbe or kill infected cells Cytolytic T cells kill infected cells with microbes (eg Viruses)
- 15. Comparison Between Innate and Acquired Immunity Innate Immunity: 1st and 2nd line of defense Immediate response with no improvement with repeated exposure React against microbes but not against noninfectious substances or host tissue Adaptive or acquired immunity (3rd line of defense) Specificity: ability to recognize different microbes (self/non self recognition) Flexibility (adaptability): ability to recognize newly evolved microbes (diversity) Memory: ability to remember previous responses and to react more quickly and more intensely
- 16. Development of cells of the immune system
- 17. Immune cells
- 18. Cells of the immune system Lymphocytes B and T cells (Th/CD4 and Tc/CD8 cells) Natural killer cells (NK cells) Antigen presenting cells B cells, monocytes/macrophages, dendritic cells Cells that produce inflammatory mediators (granulocytes) Neutrophils, basophils, eosinophils, mast cells Important in helminth and protozoan infections Involved in allergy
- 19. Immune system Antigen A toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies It can also be defined as non-self substances (cells, proteins) that are recognized by immune cells, thereby eliciting an immune response. Antibody Proteins found in blood and produced in response to a specific antigen They are released by B lymphocytes. A.k.a immunoglobulins. Cytokines Substances / proteins made by certain immune and non-immune cells that have an effect on the immune system important in cell to cell communication. Produced by a wide variety of cells including immune system cells. Classified according to action, eg chemokines- attract cells to areas of inflammation
- 20. Types of immunity Active immunity Active Immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Active immunity can be acquired through natural immunity or vaccine-induced. Passive immunity the short-term immunity which results from the introduction of antibodies from another person or animal It is immediately available but does not last long. ***reading assignment, differences between active & passive immunity