BASIC IMMUNOLOGY contains pathology .pptx

Pathology

1. BASIC IMMUNOLOGY , NATURAL AND ACQUIRED IMMUNITY AND IMMUNITY RESPONSE LECTURER TAMARA NWOKOLO

2. The  immune system  is a remarkable network of organs, cells, and proteins that work together to protect our bodies from harmful invaders. Innate Immune System : This  is our first line of defense. It provides  generalized protection  against a wide range of pathogens without prior exposure. Components include: Physical barriers : Skin, mucous membranes, and secretions. Phagocytes : Cells (such as neutrophils and macrophages) that engulf and destroy pathogens. Natural killer (NK) cells : Detect and eliminate infected or abnormal cells. Complement system : A group of proteins that enhance immune responses. Inf lammation : Triggered by tissue damage or infection, it recruits immune cells to the site.The innate system acts swiftly but lacks specificity .

3. DIFFERENCE BETWEEN INNATE AND ACQUIRED IMMUNE RESPONSE. Innate Depends on pre-formed cells and molecules Fast (starts in minutes/ hrs ) Limited specificity – pattern recognition of ‘danger signals Acquired Depends on clonal selection: i.e. growth of cells or antibodies , selected for antigen specificity. Slow (starts in days). Highly specific to foreign proteins

4. Nonspecific Immune Response (Innate Immunity) The nonspecific innate immune response provides a  first line of defense  that can often prevent infections from gaining a solid foothold in the body. These defenses are described as  nonspecific  because they do not target any specific pathogen; rather, they defend against a wide range of potential pathogens. Physical Defenses : The   skin  acts as a physical barrier to keep pathogens out. Saliva ,  mucus , and  tears  protect openings in the skin (such as the mouth and eyes) by containing enzymes that break down bacterial cell walls.

5. System of organ Factor Mechanism Mouth and intestinal tract. Saliva - lysosome & phospholipase A Low pH (HCL) – gastric juice Bile salt Alkaline pH (lower intestine) Flushing action (intestine) Mucous Phospholipase A destroys bacterial cell membrane. Kills or inhibits microbes. Prevents microbes. Eliminates microbes which have not succeeded to colonization Urogenital tract Urine (acidity) Flushing action (urine- vagina secretions) Acidic pH of vagina Mantle of vagina Low pH cleanses the urinary tract. Inhibits growth of microbes . Anatomical (physical) barriers- b) chemical factors First line of host defense (surface defenses )

6. Adaptive Immune System : The   adaptive immune system  is more sophisticated and specific. It adapts to recognize and respond to specific pathogens. Components include: B cells : Produce antibodies that target specific antigens. T cells : Coordinate immune responses and directly attack infected cells. Antigens : Molecules (often proteins) on pathogens that trigger immune responses. Memory cells : Remember previous encounters with pathogens for faster responses. The adaptive system takes longer to activate but provides long-lasting immunity .

7. Self vs. Non-Self Recognition : The immune system is able to distinguish between  self molecules  (our own cells) and  non-self molecules  (pathogens ). Failure to recognize self can lead to autoimmune diseases. Major Histocompatibility Complex. (MHC )  molecules play a crucial role in this recognition. Lymphatic System : The   lymphatic system  is intertwined with immunity. It includes lymph nodes, spleen, tonsils, and thymus. Lymph nodes filter lymph (a fluid containing immune cells) and trap pathogens. The spleen removes old red blood cells and detects infections. The thymus matures T cells .

8. Neuroimmune System : The   neuroimmune system  represents the connection between the nervous and immune systems. Neurons release neurotransmitters that influence immune responses. Stress , emotions, and circadian rhythms impact immune function . The neuroimmune system also includes hormonal signals and cytokines that participate in signaling between the immune and nervous systems The key cellular components of the neuroimmune system are  glial cells, including astrocytes, microglia, and oligodendrocytes.

9. Specific Immune Response (Adaptive Immunity) When pathogens bypass innate immune defenses, the  adaptive immune system  comes into play. This system is highly specific for individual microbial pathogens. Antigens : These are molecules found on the surface of pathogens and are unique to each pathogen. Lymphocytes : These specialized white blood cells play a crucial role in the adaptive immune response. B cells : They produce specific antibodies to a particular pathogen. T cells : They assist B cells (helper T cells) and directly kill infected cells (killer T cells ). Antigen-Specific Immune Response : Humoral Immunity : Mediated by B cells, which produce specific antibodies against pathogens. Cell-Mediated Immunity : Involves cytotoxic T cells that induce the lysis of infected cells .

10. Chemical Defenses: Inflammatory response : When a pathogen stimulates an increase in blood flow to an infected area, blood vessels expand, and  white blood cells  (phagocytes) invade the tissue to engulf and destroy bacteria. Fever : The immune system may raise body temperature to slow or stop pathogen growth and speed up the immune response.

11. What triggers the innate immune response? Triggers PAMPs – pathogen-associated molecular patterns e.g. dsRNA in cytoplasm; bacterial cell wall components. DAMPs – danger-associated molecular patterns e.g. monosodium urate; high extracellular [ATP]; reactive oxygen species (ROS). 2. Pattern-recognition receptors Extracellular danger signals. TLRs – Toll-like receptors Intracellular danger signals NLRs – NOD-like receptors RLRs - RIG-I-like receptors AIM2 - Absent in Melanoma 2.. ADD FUNCTIONS.

12. Antigens Molecules that react with antibodies or T cells. Immunogens Antigens that can initiate an immune response. Antibody They are immunoglobulin molecule in the blood and body fluids which binds specifically to an antigen . Immunoglobulins  are proteins that  act as antibodies , defending your body from harmful invaders like bacteria and viruses. They are made by white blood cells called plasma cells and circulate in your blood and other fluids, such as urine and spinal fluid

13. Five classes of Immunoglobulins. IgA Found in body secretions Contains a ‘secretory component’ which protects it from digestive enzymes. IgD Acts as an antigen receptor and antigen recognition on B cells by regulating B cell function when it encounters antigen IgE Involved in allergic response Binds to basophils and mast cells Triggers release of histamines.

14. IgG It is the most  common and versatile   type . Is the primary line of  acquired defense  against pathogens in extracellular fluids (blood, lymph, and saliva ). IgM Important in primary immune response. It is the largest antibody and provides  short-term protection  by clearing antigens from the bloodstream. It is also called a natural antibody and serves as the first line of defense againt any new infection .

15. What is the normal function of the immune system? • To identify and eliminate harmful microorganisms and harmful substances such as toxins. • By distinguishing ‘self ’ from ‘non-self’ proteins and • By identifying ‘danger’ signals (e.g. from inflammation). • The immune system must strike a balance between clearing the pathogen and causing collateral damage to the host - “immunopathology ”.

16. How does the immune system cause disease? • Immune deficiency persistent or fatal infections • A llergy • Autoimmune disease • Transplant rejection. HOW DOES AN ANTIBODY KILL A VIRUS? Four important mechanisms: 1 ) Binds to virus and prevents attachment to cell. 2 ) Opsonization : virus-Ab complex is phagocytosed by MF . 3 ) Complement-mediated lysis of enveloped viruses. 4 ) Antibody-dependent cell-mediated cytotoxicity (ADCC), mediated by natural killer (NK)-like cells

17. How does the immune response clear a pathogen? Cytotoxic T lymphocytes (CTLs) kill infected cells. Antibodies bind to pathogens: the complex is destroyed or ingested by cells. How does a T cell meet its antigen? Antigens are taken up by specialized antigen-presenting cells and transported from the tissues into secondary lymphoid organs, where they meet T cells . What happens when the antigen is removed? Most lymphocytes that have proliferated recently will die after fulfilling their function. Some survive as memory cells.

18. Vaccines: Vaccination provides acquired immunity by exposing the immune system to harmless forms of pathogens, allowing it to develop specific defenses. In summary, nonspecific defenses act as the  first line of protection , while specific immune responses are the  third line of defense  and are triggered by antigens. Together , these systems work harmoniously to safeguard our bodies against a wide array of threats. What is the second line of defense?.