Chapter 17: Basic Principles Of Adaptive Immunity And Immunization Flashcards
Acquired defenses
Require exposure to an antigen to be activated
Actively acquired
Body makes it’s own antibodies
- take longer to get started, provide long lasting protection
Passively acquired
Give ready made antibodies that came from another source
- immediate but short lived protection
Active natural
Exposure to infectious agent
- ex: bacteria or virus
Active artificial
Vaccine, weakened or killed pathogen
Passive natural
Maternal antibodies through childbirth or breast milk
Passive artificial
Injecting antibodies into someone from another source
- ex: antisera to cure venom from snake bites
Antigen
Antibody generating molecule
- a substance (protein/pathogen) that the body sees as foreign and mounts an immune response against
Epitope
Antigenic determinant
- site on antigen where antibodies bind
Hapten
Small molecule that can serve as an antigen when combined with a large protein and trigger an immune response
Humoral immunity
- Carried out by antibodies circulating in blood
- most effective against antigens outside of body cells
- B lymphocytes originate in bone marrow and mature there
- create antibodies
Humoral immunity mechanism
- B cell recognizes and binds to a specific antigen
- B cell is activated or sensitized
- B cell divides (proliferates into many clones) into plasma cells and B memory cells
- Plasma cells make antibodies specific for original antigen
- antibodies bind to antigen and mark it for destruction
Cell mediated immunity
- occurs at the cellular level
- most effective against antigens that have entered body cells (virus infected, or abnormal/cancer cells)
- T lymphocytes differentiate in thymus
General properties of immune responses
- self vs no self
- specificity
- diversity
- memory
Self vs nonself
The ability to recognize normal host substances as self and foreign substances as nonself
- Developed early in development
- colonial deletion: destroys lymphocytes that recognize self
Specificity
Each adaptive response to foreign substances is different
- one lymphocyte can only recognize one antigen
Diversity
Body can recognize and respond to over a billion antigens
Memory
Recognition of antigens previously exposed to leads to stronger, faster response
Antibody (immunoglobulin) anatomy
- Y shaped protein
- 4 polypeptide chains, 2 heavy, 2 light
- chains are held together with disulfide bonds
- constant region: determines antibody class
- variable region: contains antigen binding site
- antigen binding site
Immunoglobulin G (Ig G)
- Monomer
- Most abundant in blood
- only ig that can pass through the placenta
Immunoglobulin A (Ig A)
- Dimer
- 2 Y units liked by 1 chain
- Secretory
- Found in body secretions (saliva, tears, mucous)
Ig M
- Pentamer
- 5 units linked by a J chain
- Potent agglutinater (cell clumping)
- Found in serum and B cell membrane
Ig E
- Monomer
- Involved in allergic reactions
- Releases histamine
- Found in serum and extracellular
Ig D
- Monomer
- Found on surface of B cells
- Not sure what it does
Primary response
- First encounter with pathogen
- Create memory cells
- Response takes 5-10 days
Secondary response
- Only occurs if the same antigen enters the body again
- Faster, stronger response
- Takes 1-2 days
T independent antigens
- Only produce Ig M antibodies
- No memory cells are formed
T dependent antigens
- Requires helper T cells to activate B cells
- Produces memory cells
- Produce IgG antibodies
Antigen antibody complex reactions
Agglutination Neutralization Opsonization Activation of complement Precipitation
Agglutination
Cell clumping of microbes
- destroyed by phagocytes
Neutralization
Binds to toxin so the toxin can’t bind to other cells
- destroyed by phagocytes
Complement mediated effects
By membrane attack complexes
Opsonization
Antibodies coat the surface of pathogen and enhance adherence in phagocytosis
Precipitation
Soluble antigen precipitates out and is destroyed by phagocytes
Antigen processing
T cells can only by activated by coming into contact with an antigen presenting cell (APC)
Antigen presenting cells
B cells
Macrophages
Dendritic cells
- last two digest antigens and put pieces on their surface so T cells can “see” them
MHC
Major histocompatability complex
MHC I
- Found on all cells
- Activate cytotoxic T cells
MHC II
- Found on antigen presenting cells
- Activate helper T cells
Helper T cells
- CD4 cell
- Activated by contact with antigen in - - MHC II on APC surface
- Releases cytokines (draw WBCs to the area and activate other cells)
Helper T 1 cells
- Enhance innate response by triggering inflammation and activating macrophages
- Enhance cell mediated immunity by activating Tc cells
Helper T 2 cells
Enhance humoral immunity by activating B cells
Cytotoxic T cells
- CD8 cells
- Directly kill abnormal (virus infected or cancerous) cells
- Activated by APC with MHC I on surface
- Contain perforins
Perforins
Destructive enzyme that pokes holes in abnormal cell membranes which cause cell lysis
Memory T cells
T cells that have previously encountered and responded to their antigen
- Also known as T lymphocyte or antigen experienced T cell
Delayed hypersensitivity T cell
- Involved with the delayed immune response (overreact)
- Release chemicals that intensify immune responses
Factors modifying immune system health
Genetic factors Age Season Diet Exercise Sleep Pregnancy Medications Trauma Environment
