CH 16 17 HOST DEFENSES 1 Stephanie Lanoue

CH 16 & 17 HOST DEFENSES 1 Stephanie Lanoue

THE CONCEPT OF IMMUNITY Learning Objectives 16 -1 Differentiate innate and adaptive (acquired) immunity. 2

IMMUNITY What is immunity exactly? ability to ward off disease What happens when we cannot ward off disease? Then we have susceptibility or the lack of resistance to a disease. We can get sick. 3

BIG PICTURE: IMMUNITY AND LEVELS OF DEFENSE 4

TYPES OF IMMUNITY Innate immunity – _____ line of defense; defenses against any pathogen; rapid, present at _______ � Nonspecific defense mechanisms that come into play immediately or within hours of an antigen’s appearance in the body � Includes physical barriers like skin, chemicals in the blood, and immune system cells that attack foreign cells in the body Adaptive or acquired immunity – _______ line of defenses; more _______ than innate immunity or resistance to a specific pathogen; slower to respond, creates immunological memory (the basis of vaccination) 5

DEFENSE MECHANISMS The Immune system has __ lines of defense against foreign pathogens 1. Physical and chemical barriers (falls under Innate Immunity) 2. Nonspecific Resistance (falls under Innate Immunity) 3. Specific Resistance (falls under Acquired Immunity) 6

INNATE DEFENSE (FIRST LINE OF DEFENSE) - PHYSICAL FACTORS Cilia transports ____ trapped in mucus away from the lungs Earwax ____ microbes from entering the ear Urine cleans the urethra via flow Vaginal secretions move microorganisms out of the vaginal tract Vomiting, diarrhea Skin – dead cells in the stratum corneum help protect against pathogens; periodic shedding of that stratum removes microbes 7

INNATE DEFENSE (FIRST LINE OF DEFENSE), CONT - CHEMICAL FACTORS � Lysosomes (breaks cell walls) – tears, saliva, and sweat glands (produce perspiration) ______ microorganisms Sebaceous glands on the skin produce oil, called _____ Moist hairs, protective film over skin Fatty acid, p. H 3 to 5, discourages growth of microbes Gastric juice in the stomach destroys bacteria and most toxins. HCL (chief component of stomach acid) provides a very low p. H 1 – 2. 0 Saliva dilutes the number of microorganisms and washes teeth and mouth 8

INNATE DEFENSE (FIRST LINE OF DEFENSE), CONT - NORMAL MICROBIOTA Normal microbiota ______ with pathogens via microbial antagonism � Produce substances harmful to pathogens � Alter conditions that affect pathogen survival Probiotics: live microbial cultures administered to exert a _____ effect 9

BIG PICTURE: IMMUNITY 10

INFLAMMATION Learning Objectives 16 -12 Describe second line defenses. 16 -13 Describe inflammation; and the cause and effects of fever. 11

SECOND LINE OF DEFENSE – NONSPECIFIC RESPONSE (INNATE IMMUNITY), CONT Tissue damage triggers _______ defensive responses _______ signs and symptoms of infection: redness, pain, heat, and swelling (edema) Inflammation function: � Destroys injurious agent or limits effects on the body � Repairs and replaces tissue damaged by the injurious agent 12

SECOND LINE OF DEFENSE – NONSPECIFIC RESISTANCE (INNATE IMMUNITY), CONT. Acute inflammation � Cause of inflammation flares ______ but is removed rather quickly Chronic inflammation � Cause of inflammation is difficult to remove, longer period of time 13

INFLAMMATION PROCESS 1. Vasodilation � Vasodilation Increase permeability of blood vessels Edema, accumulation of fluid Chemical such as histamine � Blood _____ Prevent microbes from spreading � Abscess Dead cells and body fluid 14

Figure 16. 9 a-b The process of inflammation. Tissue damage Bacteria Epidermis Blood vessel Dermis Nerve Subcutaneous tissue Vascular reactions and phagocytosis Chemicals such as histamine, kinins, prostaglandins, leukotrienes, and cytokines (represented as blue dots) are released by damaged cells. Blood clot forms. 15 Abscess starts to form (orange area).

INFLAMMATION PROCESS Phagocyte migration and phagocytosis 2. Phagocyte sticks to ______ surface of endothelium � _______ between endothelial cells of the blood vessels o reach damaged area � Phagocytosis to destroy microorganism � 16

Figure 16. 9 b The process of inflammation. Blood vessel endothelium Monocyte Margination—phagocytes stick to endothelium. RBC Bacterium Diapedesis—phagocytes squeeze between endothelial cells. Phagocytosis of invading bacteria occurs. Macrophage Neutrophil 17

Figure 16. 9 c The process of inflammation. (c) Tissue repair Scab Blood clot Regenerated epidermis (parenchyma) Regenerated dermis (stroma) 18

FEVER Bacterial or viral infection Body, _____ temperature 39 ˚ C (102. 2˚ F) Hypothalamus is normally set at 37°C (98. 6 F) Phagocytes release cytokine, cause hypothalamus increase the temperature Constricting of blood vessels Increases metabolism rate 19

SPECIFIC RESISTANCE (ADAPTIVE/ACQUIRED IMMUNITY) Relies on antigens (specific proteins found in foreign microbes). Antigens: substances that cause the production of _____ � Usually components of invading microbes or foreign substances Produces an immune response 20

Major Types of Immune Cells 1. Cytotoxic T cells – these cells ____ cytotoxin which triggers destruction of the pathogen’s DNA; creates holes in the pathogens plasma membrane. The holes cause the pathogen to lyse (rupture). 2. Helper T cells – these cells secrete interleukin which stimulates cell division of ___ and B cells. In other words, these cells recruit even more cells to help fight the pathogen. 3. Memory T cells – these cells remain dormant after the initial exposure to an antigen. If the same antigen presents itself again, even if its years later, the memory cells are stimulated to convert themselves into cytotoxic T cells and help fight the pathogen 21

FIGURE 17. 1 DIFFERENTIATION OF T CELLS ANDB CELLS. Stem cells develop in bone marrow or in fetal liver Stem cell (diverges into two cell lines) Red bone marrow of adults Thymus Differentiate to B cells in adult red bone marrow Differentiate to T cells in thymus T cell B cell Migrate to lymphoid tissue such as spleen, but especially lymph nodes 22

THIRD LINE OF DEFENSE, SPECIFIC DEFENSE, CONT The immune system distinguishes __ ______ of foreign substances: � 1 group consists of antigens that are _______ circulating in the body (these include molecules, viruses and foreign cells). � 2 nd group consists of ‘self’ cells that display proteins known as MHC proteins (these proteins can originate from antigens that have been engulfed and broken down or from virus-infected and tumor cells that are actively synthesizing foreign proteins 23

SPECIFIC DEFENSE CONT. Depending on the kind of foreign invasion, __ different immune responses occur: 1. humoral (or _______ mediated response) – involves__ cells that recognize antigens or pathogens that are circulating in the lymph or blood NOTE: “humor” is a medieval term for body fluid) 2. Cell mediated response – involves mostly __ cells and responds to any cell that displays MHC markers, including cells invaded by pathogens, tumor cells or transplanted cells 24

HUMORAL IMMUNITY CONT Produces antibodies that combat foreign molecules known as _____ B lymphocyte (B cells) � B cells develop from ____ bone marrow � B cell receptors recognize antigens and make antibodies � Specific receptor for recognition of specific antigen 25

ANTIGENS AND ANTIBODIES Antibody � Globulin proteins, immunoglobulin (Ig) � Response to ____ � Recognize and bind to antigen 26

CELLULAR IMMUNITY CONT Cellular immunity (_____-mediated immunity) � Produces ___ lymphocytes Recognize antigenic peptides processed by phagocytic cells Mature in the thymus �T cell receptors (TCRs) on the T cell surface contact antigens, causing the T cells to secrete cytokines instead of antibodies � T cells response to intracellular pathogens Best for fighting with viruses and some fungi 27

Figure 17. 20 The Dual Nature of the Adaptive Immune System. 28

ADAPTIVE (ACQUIRED) IMMUNITY ______ � When a person exposed to microorganism and the immune system responds Passively � When antibody transferred from one person to another 29

Figure 17. 18 Types of adaptive (or acquired) immunity. 30