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Cellular Immunity
- Is due to T cells
- Eliminates intercellular pathogens
- Transplanted tissues
- Cancer
- Kills infected host cells
- Helps macrophages kill phagocytosed pathogens
- Difficult to passively transfer
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Types of Effector T Cells
- CD8 are killer T cells (Tc)
- CD4 are Helper T cells (Th)
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Antigen Presenting Cells
Present extracellular antigen on MHC II
Types - Dendritic cells, Macrophages, B cells, CD4 T cells bind and then "help"
All cells present intracellular antigen on MHC I and CH8 T cells bind, then "kill"
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MCH proteins
- MCH proteins = tissue typing antigens
- Class 1 MHC is on all nucleated cells - presents antigen on Tc (CD8)
Class 2 MHC is on professional Antigen Presenting Cells - presents antigen to Th1 and Th2 (CD4)
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Where does MHC1 cells load?
- MHC1 - loads in the golgi
- Loads with "self" molecules
- Binds with CD8 cells
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Where do MHC2 cells load?
- They load out side the golgi in a vesical.
- Loads with "non-self" molecules
- Binds with CD4 cells
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T cell development
- Develop in the Thymus - TCR are generated randomly in those T cells
- TCR must bind MHC 1 or MHC 2 for the T cell to survive - Cells that do not bind are signaled to undergo apoptosis
- Because Tcells are selected for their ability to bind self MHC, foreign MHC (transplants) trigger T cell rejection
- Immature T cells binding too tightly to self peptide on self MHC are also killed.
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T cell immunity
*test questions*
- Tc (cytotoxic (killer) T cells = CD8 recognize and kill virus-infected host cells
- Th1 cells = CD4 signal infected macrophages to kill pathogens in their pagosomes
- Th2 cells = CD4 signal B cells to divide and make antibodies
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Cytotoxic T cell (Tc, CTL)
- Tc go to the infection site and find and kill virus-infected cells
- They kill by releasing perforin makes pores in target cell) and granzymes (cause apoptosis)
- Tc also kill tumor cells
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TB testing
- Skin testing for TH1 function or delayed type hypersensitivity
- as small amount of antigen is injected under the skin and a reaction os recorded
- if you have a positive reaction it means your body has been infected by TB and now have antibodies for it.
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B cell activation
Antigen signal and Th2 signal
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Vaccination
Stimulate with harmless but similar antigen to generate memory cells and antibody
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Types of vaccine used in US
- Whole cell
- Live attenuated (weakened) virus
- Killed virus
- Subunit / Toxoid
- Recombinant
All will generate active immunity
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Whole cell vaccines
- Killed cell or inactivated virus is heated
- Dead, but still has antigenicity
- is injected and iummunity starts but pathogen can not multiply
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Live attenuated virus
- Can replicate in host
- Induces Tc Cells and antibodies
- Unsafe for immunosuppressed people
- Example: MMR
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Inactivated virus or bacterium
- Cannot replicate in host
- Safe, induces neutralizing antibodies
- Example: Rabies, Influenza
- "killed" vaccine
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Subunit vaccines
- Parts of pathogen - careful as to what subunits used
- Safe, generate antibodies
- Example: Pertussis (acellular) Pneumococcal pneumonia (capsule)
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Toxoid vaccines
- Inactivated toxin molecules
- Safe, generate neutralizing antibodies
- Example: diphtheria, tetanus
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Recombinant vaccine
- The use of a plasmid attached to a vector
- Example: Hepatits B virus
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DNA vaccine
- Still under development
- injecting a plasmid directly into and changing our own DNA to be resistant
- Currently used for horses
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Allergies and autoimmunity
- Allergies are IgE (antibody) immune response to harmless antigens
- The immune response causes the disease - Hypersensitivity
- Other hypersenstivities are caused by IgG or by Th1 or Tc activities
- Autoimmune reactions occur against self antigens
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Hypersensitivities Type 1: Allergy
- Immediate hypersensitivity
- Reaction in 30min
- Inflammation
- Symptoms depend on where allergen enters and how severe the immune response is
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Types of common allergens
- Pollens
- Pet dander
- Dust mite feces
- Food antigens
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Hypersensitivities Type 2:
- IgG/IgM antibodies bind RBC antigens
- Complement is activated, lyses RBC
- ADCC: macrophages or NK cells bind antibody-coated RBC and kill them
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Types of type 2 hypersensitiities
- Rh - mother having a Rh + fetus the body will attack the fetus
- Medication allergies
- Mismatched blood (transfusion reaction)
- Rheumatic fever- occurs after infection (Strep Throat)
- Autoimmune hemolytic anemia - Body attacks own RBCs
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