Immune system. Nonspecific response: inflammation. Inflammation : the beginning. Nonspecific immunity vs. Adaptive immunity

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Rhoda Bryan
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1 Immune system Body must resist disease in order to function Defends against pathogens, identifies and destroys abnormal cells. The primary pathogens are bacteria and viruses. Nonspecific immunity vs. Adaptive immunity Nonspecific responses work immediately - 1st line of defense. Neutrophils, macrophages, inflammation, MAC attack Adaptive immunity specifically targets certain pathogens to which the body has been exposed B and T lymphocytes, antibodies Nonspecific response: inflammation Redness and warmth Blood flow due to vasodilation Swelling Increased capillary permeability Pain Nociceptors stimulated by fluid pressure inflamed knee Inflammation : the beginning First response involves cells already in nearby tissue: macrophages and mast cells Macrophages eat bacteria Triggered by infection, mast cells secrete histamine, causing vasodilation Fibrin walls off infection Mast cells in tissue Guided by chemotaxins, neutrophils and monocytes go to the area 1

2 How do phagocytes know what to eat? Bacteria get labeled for destruction by opsonins Opsonins are made from complement cascade, helper T cells, antibodies Phagocytes also send signals They present antigens to helper T-cells to induce a specific response Bacteria acquire opsonins, getting labeled for macrophage to engulf it histamine plasma proteins (including opsonins and chemotaxins) Review Phagocytes: stimulate histamine release, trigger clotting cascade, release pyrogen which causes fever, induce more WBC 2

3 What do those plasma proteins do? Some are clotting proteins..clotting cascade! Nonspecific response : Complement system Complement = cascade of plasma proteins Some are antibodies! (discussed soon) Some are part of the complement system! (discussed now ) Cascade activated by molecules on surface of bacteria or antibodies Complement proteins are opsonins, chemotaxins or form MAC attack MAC Nonspecific response: What about viral infections? Infected cells release interferon Causes neighboring cells to produce virusfighting enzymes Attracts natural killer cells Nasty virus Host Interferon 3

Adaptive immune response Also fights viral and bacterial infections but uses B and T lymphocytes found in lymph Pathogens have particular antigens, which

B cell response B lymphocytes respond to bacteria and toxins An antigen stimulates some specific B cells to become plasma cells and produce antibodies Contact

4 Adaptive immune response Also fights viral and bacterial infections but uses B and T lymphocytes found in lymph Pathogens have particular antigens, which induce a specific response from B and T cells. B cell response B lymphocytes respond to bacteria and toxins An antigen stimulates some specific B cells to become plasma cells and produce antibodies Contact with antigen can occur via macrophages Only cells with the antigen are attacked. antigens B cell response How antibodies work antigen bacteria binding site for this specific antigen Once labeled, bacteria killed by: MAC attack Phagocytosis Killer cells Labels cell to be killed 4

Immunological Memory Memory cells activated on secondary exposure response is larger and faster What about T cells?

5 B cell response When specific B cells are activated, they multiply Result of labeling Some cells become memory cells, stored in case of a subsequent infection Different B cell clones Many plasma cells Antigen fits with this B cell Some memory cells Making antibodies Immunological Memory Memory cells activated on secondary exposure response is larger and faster What about T cells? T cells recognize infected or cancerous body cells (cell-mediated) When triggered, specific T cells divide. Killer T cells release chemicals to kill the bad cell vaccination 5

6 What triggers T cells? T cells activated by detecting a combination of self marker and pathogen (or cancer) marker Protein coat has antigen Killer T cell Foreign viral antigen Self-antigen 2 Viral antigen is displayed on surface of host cell with self-antigen Virus invaded host cell 3 Killer T cell recognizes and binds with a specific foreign antigen complex Antigen complex Virus invaded host cell 6

7 Helper T cells 4 Killer T cell releases chemicals that destroy cell Helper T cells do not kill cells, but amplify effects of other WBCs: Enhance production of T and B cells, make chemotaxins for phagocytes Master switch for immune response T-lymphocyte Fig d, p. 326 Helper T cells Helper T cells are involved with B cell response as well Self markers MHC genes The MHC is a set of genes that code for self markers Matching MHC markers - organ transplants 7

8 Allergies: adaptive immunity gone wrong Reactivity to a harmless substance in environment Common triggers: pollen, molds, bee stings, dust, fur, mites, penicillin Allergies: adaptive immunity gone wrong Specific B cell clones Allergens IgE antibodies Allergies involve a particular type of antibody IgE antibodies IgE antibodies trigger mast cells and basophils to produce histamine and other chemicals at the site of the allergens Allergies: adaptive immunity gone wrong Hives - allergens on skin Hay fever - allergens in nasal passages Asthma - allergens in airway Allergies: adaptive immunity gone wrong Anaphylactic shock - when large amounts of histamines and other chemicals enter the blood. circulatory failure airway constriction 8

9 What makes some diseases autoimmune diseases? Immune system wrongly attacks body cells Rheumatoid arthritis joints are constantly inflamed How can I boost my immune system? Vitamin D helps trigger T cell response Sleep Diet Exercise Blood groups ABO blood types are named by antigens on the surface of RBCs: A, B, AB, or O (neither antigen). People acquire antibodies for the blood antigens they do not have on their RBCs. Blood type O : universal donor (no antigens). Blood type AB : universal recipient (no antibodies) Why are there so many different blood types? There are 23 different blood group systems and hundreds of types 8 types relevant to blood compatibility Other animals evolved different types as well Type A is oldest, B started 3.5 million y.a., O started 2.5 million y.a. (helps w malaria) Functions of A and B types unknown Incompatibility only relevant w transfusions 9

10 Preventing entry of pathogens Mucus and acid are your friends Tears wash away pathogens Oily waxy secretions trap pathogens Cilia of mucus elevator in airway moves pathogens up to be swallowed Acid in urethra and vagina prevent infections Mucus traps pathogens which are swallowed or sneezed away Friendly bacteria prevent other bacteria from growing Macrophage in lung tissue Stomach has acid to kill swallowed pathogens Outer epidermis is mainly dead cells that are hard for pathogens to grow on or penetrate Underlying dermis contains sweat glands and oil glands Skin Combining non-specific and adaptive immune response Bacterial infection: At first: phagocytes, histamine release, inflammatory response Inflammation brings phagocytes, plasma proteins (complement system, clotting proteins) Bacteria antigen stimulates helper T cells, B cells get activated: antibodies Bacteria get labeled w/antibodies, killed by complement, macrophages, killer cells. 10

11 Combining non-specific and adaptive immune response Viral infection: Virus inside body cells do not trigger macrophages, B-cells, or complement. Virus-infected or cancerous cells release interferon, signaling neighboring cells and attracting natural killer cells, macrophages, complement. Virus out in the open can be attacked. Antigen-self combination triggers T-helpers, which help stimulate killer T cells (takes days) and attract macrophages to the area. 11

The Immune System. 2 Types of Defense Mechanisms. Lines of Defense. Line of Defense. Lines of Defense

The Immune System. 2 Types of Defense Mechanisms. Lines of Defense. Line of Defense. Lines of Defense The Immune System 2 Types of Defense Mechanisms Immune System the system that fights infection by producing cells to inactivate foreign substances to avoid infection and disease. Immunity the body s ability