The Body’s Defenses Chapter 43

Interstitial fluid Adenoid Tonsil Blood capillary Lymph nodes Spleen Fig. 43-7 Interstitial fluid Adenoid Tonsil Blood capillary Lymph nodes Spleen Tissue cells Lymphatic vessel Peyer’s patches (small intestine) Appendix Figure 43.7 The human lymphatic system Lymphatic vessels Lymph node Masses of defensive cells

Pathogen Pathogen: An agent of disease. A disease producer. The term pathogen most commonly is used to refer to infectious organisms. These include bacteria (such as staph), viruses (such as HIV), and fungi (such as yeast). Less commonly, pathogen refers to a noninfectious agent of disease such as a chemical.

Fig. 43-1 Fig 43.1 How do immune cells of animals recognize foreign cells? For the Cell Biology Video Leukocyte Adhesion and Rolling, go to Animation and Video Files. 1.5 µm

First Line of Defense Second Line of Defense Third Line of Defense Fig. 43-2 Pathogens (microorganisms and viruses) INNATE IMMUNITY Barrier defenses: Skin Mucous membranes Secretions • Recognition of traits shared by broad ranges of pathogens, using a small set of receptors First Line of Defense Second Line of Defense Third Line of Defense Internal defenses: Phagocytic cells Antimicrobial proteins Inflammatory response Natural killer cells • Rapid response ACQUIRED IMMUNITY Humoral response: Antibodies defend against infection in body fluids. Figure 43.2 Overview of animal immunity • Recognition of traits specific to particular pathogens, using a vast array of receptors Cell-mediated response: Cytotoxic lymphocytes defend against infection in body cells. • Slower response

1st line of Defense Nonspecific Barrier Skin Mucous Cilia Stomach Acid Lysozyme Cilia Stomach Acid

2nd Line of Defense Inflammatory Response 1st line has been penetrated!!! Inflammatory Response Vasodilation Histamine Released by: Basophils & Mast Cells Prostaglandins – Promotes Blood Flow Chemokines – attracts phagocytes Neutrophils  destroy microbes Monocytes  into Macrophages  large # of microbes Pyrogens – increases temperature Interferons – block against viral infections

3rd Line of Defense Specific Response

Acquired immunity defends against infection of body cells and fluids Acquired immunity has two branches: the humoral immune response and the cell-mediated immune response Humoral immune response involves activation and clonal selection of B cells, resulting in production of secreted antibodies Cell-mediated immune response involves activation and clonal selection of cytotoxic T cells Helper T cells aid both responses

Figure 43.16 An overview of the acquired immune response Humoral (antibody-mediated) immune response Cell-mediated immune response Key Antigen (1st exposure) + Stimulates Gives rise to Engulfed by Antigen- presenting cell + + + B cell Helper T cell Cytotoxic T cell + + Memory Helper T cells + + + Figure 43.16 An overview of the acquired immune response Antigen (2nd exposure) + Memory Cytotoxic T cells Active Cytotoxic T cells Plasma cells Memory B cells Secreted antibodies Defend against extracellular pathogens by binding to antigens, thereby neutralizing pathogens or making them better targets for phagocytes and complement proteins. Defend against intracellular pathogens and cancer by binding to and lysing the infected cells or cancer cells.

Active and Passive Immunization Active immunity develops naturally in response to an infection It can also develop following immunization, also called vaccination Passive immunity provides immediate, short-term protection Breast Milk Injection of Antibodies