Immunity PDF

Today’s Learning Objectives Compare and contrast innate and adaptive immunity Describe the role of T cells and B cells in immunity Describe local inflammation  Think-Pair-Share Game of Thrones A very rich distant relative has left you a big castle. You...

Today’s Learning Objectives Compare and contrast innate and adaptive immunity Describe the role of T cells and B cells in immunity Describe local inflammation  Think-Pair-Share Game of Thrones A very rich distant relative has left you a big castle. You need to make sure it is protected so that nearby families will not try and take this from you. How would you defend your castle? What defenses would you add to make sure nobody can still it?  Body Defenses What are some structures/organs/cells that you think contributes to your body’s nonspecific defense system? What are some structures/organs/cells that you think contributes to your body’s specific defense system? Innate Immunity (nonspecific) 15-4 Innate (Nonspecific) Immunity Local response Protect against invasion of a wide variety of pathogens and toxins Born with it; defense against pathogens without exposure Doesn’t care what type of pathogen is involved. e.g. bacteria, viruses, dust, bugs Includes external & internal defenses 1. Epithelial barriers 2. High acidity of secretions 3. Phagocytosis 4. Inflammation, fever  Nonspecific Phagocytosis Neutrophils: 1st to arrive at infection site Macrophages Organ-specific phagocytes in liver, spleen, lymph nodes, lungs, brain Line sinusoids of liver, spleen, lymph nodes; remove pathogens Chemokines released from tissue attract phagocytes by a process called chemotaxis. Phagocytes move out of capillaries through fenestrations by diapedesis 15-7  Interferons Polypeptides produced by cells infected with virus Provide resistance to viral infection in nearby cells Inhibits ability of virus to replicate & assemble new virus particle 15-11 Adaptive Immunity (Specific) 15-14  Adaptive Immunity Acquired ability to defend against specific pathogens by prior exposure to those pathogens AKA Learned Response Systemic: not restricted to local infection site Has memory: recognizes, mounts a stronger attack on previously encountered pathogens 15-15  Two Types of Adaptive Immunity 1. Cell-mediated: Using T cells to present antigens to killer cells - Attack infected host cells (by virus or fungi), cancer cells, and foreign cells 1. Antibody-mediated: Using B cells to make antibodies to tag antigens for death - Attack bacteria and viruses Life of a B cell Begin as stem cell in bone marrow Stay in marrow Mature B cell (gain receptors) Lymph & blood (Humoral) Introduced to antigen Activated B cell 1. Plasma cells: make antibodies 2.Memory cells: for second exposure B lymphocytes 1. B cells have receptors to notice foreign antigens Usually are proteins of foreign viruses, bacteria, allergens 2. After recognition of matching antigen, B cells divide and clone 3. They become plasma cells or memory cells Memory cells They “remember” the antigen The first time was a primary response The second time is a secondary response A more rapid, potent, longer lasting response Often see no symptoms of foreign antigen  Primary and Secondary Responses On 1st exposure to pathogen, there is latency of 5-10 days before specific antibodies are made (= primary response) – Antibody levels plateau after few days and decline after a few weeks Subsequent exposure to same antigen causes secondary response – Antibody production is much more rapid and sustained 15-63  Antibodies AKA immunoglobulins (proteins) Part of gamma globulin class of plasma proteins Antibodies have same basic structure but their differences provide for antibody specificity 15-31 Table 15.6 Complement Complement the action of antibodies. Activated by pathogens (nonspecific) or exposure to antibodies (specific) When activated, proteins build a pore in the foreign cell. The pore is called MAC (membrane attack complex) Osmotic influx of water, cell swells and burst. B cells and T cells Life of a T cell Begin as stem cell in bone marrow Go to thymus Mature T cell (gain receptor) Lymph & Blood Introduced to antigen Sensitized T cell 1. Helper T cell 2. Cytotoxic T cell 3. Suppressor T cell  T lymphocytes Cell-mediated immunity Mature in thymus Activated only by antigens presented by antigen-presenting cells, e.g. macrophages, dendritic cells & B lymphocytes T cells activated: Promote action of macrophage & lymphocytes  Types of T cells Helper T cell (CD4) 60-80% of T cells are helper T cells Secrete proteins to assist other parts of system B cell growth factor Interleukins for T cell growth Suppressor/regulatory T cell Prevents overactive immune responses  Cytotoxic/Killer T cell (CD8) Releases perforin to make pore in foreign cell, causes osmosis and destruction Transplant rejection, defends from virus, fungus B cells and T cells  Review Question ____ are involved in shutting down the immune response after infection A. Helper T-cell B. Cytotoxic T cell C.Plasma cells D.Suppressor T cell  Self-Antigens Human cells have our own (many) surface proteins Our immune cells do not attack our own proteins Our cells in another person’s body can trigger an immune response because they are foreign – Restricts donors for transplants  T cells recognize MHC The pathogen is engulfed by a phagocyte A piece is put onto a protein in the membrane, Called MHC Molecules on cell membranes present in different combinations in different people T cell recognizes MHC plus antigen Activates specific T cell response to specific antigen MHC molecules Found on all cells Occurs in lymph node Signals infected cell  Interaction between class-2 MHC & Helper T cell Occurs in lymph node  Think-Pair-Share Why would it be beneficial to require the activation of B cells and Cytotoxic T cells by Helper T cells?  Autoimmune diseases Failure of immune system to recognize & tolerate self-antigens Autoreactive T cells are formed and B cells produce autoantibodies e.g. Myasthenia Gravis: antibodies to nicotinic cholinergic receptors on skeletal muscle Afflicts women twice as often as men Fig. 15.16 Interaction between class-1 MHC & Killer T cell Review Question Which of these statements about class-2 MHC molecules is false? A. They are found on the surface of B lymphocytes B. They are found on the surface of macrophages C. They are presented with foreign antigen by macrophages to activate T helper cells D. All of these are true Questions of the Day Explain how antibodies help to destroy invading bacterial cells. Describe the interaction between antigen presenting cell & T cell. Compare and contrast B & T lymphocytes.