 Chapter 43: Immune System

Learning Targets 1. I can explain innate immunity by:  Describing barrier defenses  Describing internal defenses 2. I can explain adaptive immunity by: describing humoral response which includes:  B cells  Plasma cells  Antibodies  Memory cells  Helper T cells  Describing cell mediated response which includes  Cytotoxic T Cells and memory cells 3. I can identify and explain parts of immune system that represent how cells communicate via paracrine communication. 4. I cam explain the difference between a primary and secondary immune response 5. I can explain the difference between active and passive immunity.

Focus Questions 1. What is the functional difference between cell mediated and humoral immunity? Why do we have both types? 2. Which blood cells are involved in cell mediated immunity? 3. Which blood cells are involved in humoral immunity? 4. Why is it that you don’t get the chicken pox, once you have already had it? 5. If you are bit by a venomous snake, what type of immunity are you given when you receive an anti venom injection? When you received your hepatitis vaccination, what type of immunity are you given?

Figure 43.2 Pathogens (such as bacteria, fungi, and viruses) INNATE IMMUNITY (all animals) Rapid response Recognition of traits shared by broad ranges of pathogens, using a small set of receptors Recognition of traits specific to particular pathogens, using a vast array of receptors Slower response Barrier defenses: Skin Mucous membranes Secretions Internal defenses: Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response Humoral response: Antibodies defend against infection in body fluids. Cell-mediated response: Cytotoxic cells defend against infection in body cells. ADAPTIVE IMMUNITY (vertebrates only)

Figure Primary immune response to antigen A produces antibodies to A. Secondary immune response to antigen A produces antibodies to A; primary immune response to antigen B produces antibodies to B. Exposure to antigen A Exposure to antigens A and B Time (days) Antibody concentration (arbitrary units) Antibodies to A Antibodies to B

Cell mediated Immunity Antigen- presenting cell Pathogen Antigen fragment Class II MHC molecule Accessory protein Antigen receptor Helper T cell Cytokines Humoral immunity Cell- mediated immunity B cell Cytotoxic T cell 321    

Figure Cytotoxic T cell 1 Accessory protein Class I MHC molecule Infected cell Antigen receptor Antigen fragment

Figure Cytotoxic T cell 12 Accessory protein Class I MHC molecule Infected cell Antigen receptor Antigen fragment Perforin Pore Gran- zymes

Figure Cytotoxic T cell 312 Accessory protein Class I MHC molecule Infected cell Antigen receptor Antigen fragment Perforin Pore Gran- zymes Released cytotoxic T cell Dying infected cell

Humoral Response Pathogen 1 Antigen-presenting cell Antigen fragment Class II MHC molecule Antigen receptor Accessory protein Helper T cell

Humoral Response Pathogen 12 Antigen-presenting cell Antigen fragment Class II MHC molecule Antigen receptor Accessory protein Helper T cell B cell Cytokines Activated helper T cell 

Humoral Response Pathogen 312 Antigen-presenting cell Antigen fragment Class II MHC molecule Antigen receptor Accessory protein Helper T cell B cell Cytokines Activated helper T cell Memory B cells Plasma cells Secreted antibodies 

 Figure Opsonization Neutralization Antibody Virus Bacterium Macrophage Activation of complement system and pore formation Complement proteins Formation of membrane attack complex Flow of water and ions Pore Antigen Foreign cell

Figure Humoral (antibody-mediated) immune response Cell-mediated immune response Antigen (1st exposure) Engulfed by Antigen- presenting cell Helper T cell Memory helper T cells Antigen (2nd exposure) B cell Plasma cells Secreted antibodies Defend against extracellular pathogens Memory B cells Memory cytotoxic T cells Active cytotoxic T cells Defend against intracellular pathogens and cancer Cytotoxic T cell Key Stimulates Gives rise to          

Figure 43.UN02 Stem cell Cell division and gene rearrangement Elimination of self-reactive B cells Clonal selection Antigen Antibody Formation of activated cell populations Memory B cells Plasma cells Pathogen Receptors bind to antigens

Figure 43.UN03