Fighting the Enemy Within! phagocytic leukocyte Fighting the Enemy Within! Immune System Big Questions: What is the purpose of a immune system? How does the immune system function? Why do animals have a more developed immune system?

Immune Systems Highly developed in mammals Two types of immunity: Innate immunity (nonspecific) Adaptive immunity (specific) What about other organisms? Lymphatic System: Production & transport of leukocytes (WBC) Traps foreign invaders

Bacteria & insects inherit resistance. Vertebrates acquire immunity. Lines of Defense 1st line: INNATE barriers broad, external defense structures “walls & moats” 2nd line: INNATE patrols broad, internal defense cells “patrolling soldiers” 3rd line: Adaptive Immunity specific pathogens targeted “elite trained units” Bacteria & insects inherit resistance. Vertebrates acquire immunity.

1st line: Examples Barrier Traps Elimination Unfavorable pH skin Traps mucous membranes, cilia, hair, earwax Elimination coughing, sneezing, urination, diarrhea Unfavorable pH stomach acid, sweat, saliva, urine Lysozyme enzyme digests bacterial cell walls tears, sweat Lining of trachea: ciliated cells & mucus secreting cells

2nd line: Examples Cells attacking ALL invaders leukocytes bacteria Cells attacking ALL invaders leukocytes phagocytic white blood cells macrophages, neutrophils, natural killer cells, dendritic cells Antimicrobial proteins Complement system Interferons inflammatory response increase in body temp. increase capillary permeability attract macrophages/neutrophils macrophage yeast

Inflammatory response Pathogen Splinter Movement of fluid Signaling molecules Macro- phage Mast cell Capillary Phagocytosis Red blood cells Neutrophil Figure 43.8-3 Major events in a local inflammatory response (step 3) 1 Histamines and cytokines released. Capillaries dilate. 2 Antimicrobial peptides enter tissue. Neutrophils are recruited. 3 Neutrophils digest pathogens and cell debris. Tissue heals.

Fevers System-wide response to infection Activated macrophages release interleukin-1 triggers hypothalamus in brain to readjust body thermostat to raise body temperature Is this a positive or negative feedback response? higher temperature helps defense inhibits bacterial growth causes liver & spleen to store iron, reducing blood iron levels bacteria need large amounts of iron to grow Septic Shock – inflammatory reaction out of control Certain bacterial infections can induce an overwhelming systemic inflammatory response leading to a condition known as septic shock. Characterized by high fever and low blood pressure, septic shock is the most common cause of death in U.S. critical care units. Clearly, while local inflammation is an essential step toward healing, widespread inflammation can be devastating.

3rd line: Adaptive Immunity B cell Specific pathogens are recognized and attacked “True Immune System” WBC’s – Lymphocytes: B cells T cells Two Processes: Humoral Immunity Cell Mediated Immunity T cell

How Are Cells/Pathogens Recognized? Surface protein markers – ANTIGENS Antigens can elicit a response from lymphocytes “self” antigens no response from WBCs Class I MHC – major histocompatibility complex protein markers on cell membrane of ALL cells

“foreign” antigens response from WBCs pathogens: viruses, bacteria, protozoa, worms, fungi, toxins non-pathogens: cancer cells, transplanted tissue, pollen, food, chemicals

Humoral Response Attacks foreign antigens in blood or lymph Antibody proteins are produced to attack specific antigen markers on pathogens B Cells types: plasma cells immediate production of antibodies rapid response, short term release memory cells continued circulation in body long term immunity

What do antibodies do to invaders?

Cell Mediated Response Attack, learn & remember pathogens hiding in infected cells recognize antigen fragments also defend against “non-self” body cells cancer & transplant cells Types of T cells helper T cells alerts rest of immune system killer (cytotoxic) T cells attack infected body cells memory T cells long term immunity T cell attacking cancer cell

Cell-Mediated Response Killer T cell binds to infected cells Secretes perforin protein causing apoptosis or lysis of infected cell Creates memory killer-T’s for further exposures

How Do Helper T Cells Work? Binds to an Antigen Presenting Cells (APC) displaying foreign antigen on cell membrane Class II MHC markers Activates itself with cytokines and clones into 1000’s Cloned Helper T’s search for specific B Cell and Killer T for the same pathogen MHC proteins displaying foreign antigens infected cell TH cell WANTED Helper T cell with antigen receptors

Helper T’s Role in Immunity “I am going to clone myself.”

What is the correct sequence in which the following occur during a primary humoral immune response? B cell activation helper T cell activation plasma cell differentiation and proliferation antibody secretion presentation of antigen on class II MHC proteins 5, 2, 1, 4, 3 d) 4, 5, 3, 1, 2 4, 5, 2, 1, 3 e) 5, 2, 1, 3, 4 5, 1, 2, 3, 4 18

What is the correct sequence in which the following occur during a primary humoral immune response? B cell activation helper T cell activation plasma cell differentiation and proliferation antibody secretion presentation of antigen on class II MHC proteins 5, 2, 1, 4, 3 d) 4, 5, 3, 1, 2 4, 5, 2, 1, 3 e) 5, 2, 1, 3, 4 5, 1, 2, 3, 4 19

2 Types: ACTIVE and PASSIVE What is Immunity? 2 Types: ACTIVE and PASSIVE

Active Immunity Must get exposed to the pathogen! Naturally – get sick Artificially – get a vaccination Both methods cause memory cells to be made for future exposures. How long does first exposure typically take to feel better? Why was the 2nd exposure so short in duration? What determines whether or not you are immune?

Primary Immune Response with B and T cell activation:

Passive immunity (antibodies not immune cells) Naturally obtaining antibodies from mother antibodies pass from mother to baby across placenta or in mother’s milk critical role of breastfeeding in infant health Artificially injection of antibodies Ex: anti-venom serum short-term immunity

HIV and AIDS Weakens Adaptive Immunity Human Immunodeficiency Virus virus infects helper T cells AIDS: Acquired ImmunoDeficiency Syndrome infections and death by opportunistic diseases pneumonia, cancers HIV infected T cell

Immune System Malfunctions Auto-immune diseases immune system attacks own molecules & cells rheumatoid arthritis Diabetes multiple sclerosis Allergies makes wrong antibody for foreign antigen allergens = proteins on pollen, dust mites, in animal saliva, food 1st exposure you are not allergic. Allergy is confirmed after subsequent exposures Anaphylaxis – most severe reaction

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