Ch 8 - Immune

Question 1

Innate vs Adaptive Immunity

Answer 1

• innate - aka nonspecific immunity
  
  • always active
  • does not attack specific pathogens
• adaptive - aka specific immunity
  
  • target specific pathogens
  • slower, but more robust and long lasting
  • holds memory
  • B cells and T cells

Question 2

Anatomy of Immune

Answer 2

• bone marrow - hematopoiesis of leukocytes (WBC)
• spleen - blood storage, activate B cells
  
  • B cells are mature but naive until they are exposed to an antigen
  • humoral immunity - B cells acting in the blood as part of active immune system
• Thymus - T cells mature
  
  • cell mediated immunity
• lymph nodes - can be location for activation of B cells
• Gut-associated lymphoid tissue (GALT) - tonsils, adenoids, Peyer’s patches, appendix

Question 3

Leukocytes

Answer 3

• granulocytes - presence of granules (contain toxic enzymes and chemicals for exocytosis)
  
  • neutrophils
  • eosinophils
  • basophils
• agranulocytes - no granules
  
  • lymphocytes - produce antibodies, modulation, targeted killing
  • monocytes - become macrophages, phagocytic
    
    • microglia, Langerhans cells, osteoclasts

Question 4

physical barriers

Answer 4

• skin (integument)
• defensins - antibacterial enzymes, found on skin
• lysozyme - bacterial enzyme, tears and saliva
• respiratory system uses mucous membranes and cilia
• GI tract - highly acidic
  
  • its own bacterial population out competes invaders

Question 5

Complement System

Answer 5

• proteins in the blood that punch holes in the bacterial cell walls to cause osmotic imbalance
• activated via classical pathway (bind antibody to pathogen) or alternative pathway (no antibodies)
• Nonspecific defense

Question 6

Interferons

Answer 6

• prevent viral replication and dispersion
• produced by cells that are virally infected
• decrease production of viral and cellular proteins
• decrease permeability of cells
• increase MHC I and II molecules to increase antigen presentation - better detection
• cause viral like symptoms

Question 7

Macrophages

Answer 7

• agranulocyte
• antigen presenting cell
• come from monocytes
• resident population - remain in a given tissue
  
  • microglia, Langerhans cells, osteoclasts
• when bacteria in the tissue:
  
  • endocytosis, digest via enzymes, present bacterial antigen
• major histocompatibility complex (MHC) - MHC II presents the antigen on the macrophage surface
• release cytokines - cause inflammation and recruit immune cells

Question 8

MHC

Answer 8

• Major histocompatibility complex
• binds antigens
• MHC I - displays “self” antigen of all nucleated cells
  
  • endogenous pathway - binds antigens from inside the cell
  • cytotoxic T cells - kill cells that present non-self on MHC I
    
    • cells that have been invaded
• MHC II - on antigen presenting cells (ex. macrophage, dendritic cells, some B-cells, )
  
  • exogenous pathway - antigens from outside the cell
  • may activate innate and adaptive immune system

Question 9

Pattern recognition receptors

Answer 9

• ex. toll like receptor
• recognize category of invader (bacteria, virus, fungus, parasite)
• on macrophages and dendritic cells
• produce most effective cytokine

Question 10

Natural Killer Cells

Answer 10

• nonspecific lymphocyte
• detect downregulation of MHC (a tactic used by viruses to avoid detection)
• causes apoptosis of cell
• cancer cells downregulate MHC - NK cells help slow cancer growth

Question 11

Granulocytes

Answer 11

• neutrophils - most populous leukocyte, short lived
  
  • phagocytic
  • chemotaxis to bacteria to find source
  • detect opsonized bacteria
• eosinophils - contain granules
  
  • allergic reactions
  • invasive parasite infections
  • release histamine, causes inflammation
• basophils - allergic responses
• Mast cells - related to basophils
  
  • in tissues, mucosa, epithelium

Question 12

dendritic cells

Answer 12

• present antigens
• induce active immune system
• have pattern recognition receptors that recognize type of invader
• phagocytic

Question 13

Antibody-Antigen Cause and Effect

Answer 13

• B cells - originate and mature in bone marrow
• activated in spleen and lymph nodes
• produce antibodies
• when antibodies secreted into blood:
  
  • 1. bind specific antigen, opsonization and attracts other WBC
  • 2. Cause aggluination, insoluble and phagocytized
  • 3. Block pathogen from entering tissue
• when a B cell surface antibody
  
  • antigen binds and activated immune cell
  • proliferate and make plasma and memory cells
• antibody on surface of mast cell
  
  • antigen binds and causes degranulation (exocytose granule contents) - release histamine

Question 14

Antibodies

Answer 14

• aka Immunoglobulins [Ig]
• Y shaped
  
  • 2 identical heavy chains
  • 2 identical light chains
  • held together by disulfide bonds
  • variable region - aka antigen binding region
    
    • polypeptide sequence that binds ONE specific antigen sequence
• clonal selection - specific B cells with correct antibody are activated by antigen of pathogen and replicates only that B cell
• hypermutation - B cells use this to find antigen binding region that has best match for antigen
• constant region (domain) - remainder of antibody
  
  • used by neutrophil, macrophages, eosinophils to initiate complement cascade
• 5 isotypes of antibodies
  
  • different isotypes used for different pathogens, locations in body, and different times
  • isotype switching

Question 15

B Cells

Answer 15

• naive B cells - not exposed to antigen, wait in lymph nodes
• plasma cells - produce large amounts of antibodies
• memory cells - stay in lymph node for future response
• primary response - initial activation takes 7-10 days
• secondary response - more rapid and robust response to same antigen
  
  • vaccinations

Question 16

T cells

Answer 16

• mature in thymus
• positive selection - mature cells that respond to antigens on MHC
• negative selection - apoptosis for cells that react to self antigens
• thymosin - peptide hormone that causes maturation, comes from thymus
• clonal selection once exposed to antigens
• helper T cells - aka CD4+ T cells - secrete lyphokines which recruit other immune cells
  
  • Human Immunodeficiency virus (HIV) is caused by loss of helper T cells
  • Acquired immunodefiviency syndrome (AIDS) - advanced HIV, very weak immune system
  • CD4+ responds to antigens on MHC II (exogenous antigens) = effective against extracellular infections
• Cytotoxic T cells - aka CD8+ T cells - kill virally infected cells by injecting toxins causing apoptosis
  
  • respond to MHC I antigens - endogenous antigens - intracellular infections
• suppressor T cells - T_reg - tone down immune response
  
  • self tolerance - turn off self reactive lyphocytes - prevent autoimmune disease

Question 17

How to fight bacterial infection

Answer 17

• bacteria enters body via laceration
• antigen presenting cell (ex. macrophage) engulf and present antigens on surface via MHC II
• release cytokines - other immune cells attracted (neutrophils and more macrophages)
• Mast cells activated - degranulate and release histamine, leaky capillaries and inflammation
• dendritic cell from skin to lymph node to activate B cells and T cells
• correct B cells proliferate (clonal selection) - plasma and memory cells
• antibodies through bloodstream to opsonize, agglutinate, and prevent bacteria from reaching other cells
• T cells - CD4+ activated - release interferons to activate macrophages. also activate B cells

Question 18

How to fight viral infection

Answer 18

• infected cell produces interferons
  
  • reduce local cells permeability, reduce transcription and translation, systemic symptoms
• present intracellular antigens on MHC I, some will be viral proteins
• CD8+ recognize MHC I antigen complex - injects toxins to promote apoptosis
• also NK cells will recognize absence of MHC I if virus downregulates MHC I
• Memory T cells retained

Question 19

Self vs nonself

Answer 19

• autoimmunity - immune system attacks cells that present self antigen
• hypersensitivity reactions - allergies and autoimmunity
  
  • allergies - immune system identifies harmless nonself antigen (ex dust, pollen) as harmful
• prevent - negative selection of T cells
• only mature B cells leave bone
• treat with Glucocorticoids

Question 20

Immunization

Answer 20

• active immunity - immune system stimulated to produce antibodies
  
  • natural or artificial
• passive immunity - transfer antibodies to individual
  
  • across placenta
  • injections

Question 21

Lymphatic System

Answer 21

• one way circulation of lymph
• thoracic duct in chest returns lymph to circulatory system via vein
• lymph nodes - along system and house immune system and excess fluid
  
  • germinal centers - lymph nodes are location of B cell proliferation and maturation
• equalizes fluid distribution
  
  • starling forces determine amount of fluid in tissues, lymphatics drains this away and back to circulatory system
  • overwelmed causes Edema
• lacteals - lymphatic vessels that carry chylomicrons (packages of fat) to the bloodstream from intestines
  
  • chyle - lymphatic fluid with lots of chylomicrons