immunity

Question 1

fx of immune system

Answer 1

1. distinguish self from non-self
   • every org makes surface cell markers for self identification
   • fetus learns how to differentiate
2. protects against pathogens
3. mobilize cells to sites of infx
4. contain infx
5. develop antigen-specific antibodies

• antigen = antibody-generator (aka pathogen)
  
  • induces immune response
  • epitope: facet of antigen
    
    • each antigen can have several epitopes
    • each epotope can generate a unique antibody

Question 2

primary lymphoid organs

Answer 2

• early in fetal development
• site of lymphocyte development
  
  • class of white blood cells
  • thymus = site of T cell maturation
    
    • T cells stimulated by antigen
  • bone marrow = site of B cell matuation
    
    • B cells secrete antibodies

Question 3

secondary lymphoid organs

Answer 3

• axillary lymph nodes
• spleen
• peyer’s patches in ileum of SI
• mesenteric lymph nodes
• inguinal lymph nodes

Question 4

1st line of defense

Answer 4

anatomical/physical & chemical barriers

• non-specific barriers
• physical:
  
  • skin
  • mucus
  • peristalsis
  • flushing (tears, saliva, urine)
  • cilia of GIT
• chemical:
  
  • acidic pH (stomach, vagina)
  • sweat
  • bile salts
  • digestive enzymes
  • non-specific IgA
  • antimicrobial peptides
    
    • paneth cells in crypts make defensins & cryptdins ➞ enzymes disrupt bacterial membranes & metabolize to prevent from growing
    • lysozyme in tears & saliva breaks bonds in cell wall of bacteria ➞ cleavage makes cell walls leaky
  • microbial: competition for space & nutrients (commensal)

Question 5

innate immunity

Answer 5

• innate & immediate
• non-specific
• leukocytes: white blood cells
  
  • neutrophils
  • monocytes in blood
  • marophages (MΦ) in tissues
  • dendritic cells (DC)
  • macrophages & dendritic cells = antrigen-presenting cells (APCs)
• cell-mediated immunity

Question 6

adaptive immunity

Answer 6

• when innate immunity fails
• MΦ & DC migrate to peyer’s patches in lymph nodes for destruction
• T cells are activated by APCs
• helper T cells activate B cells to proliferate & differentiate in antibody-secreting cells
• antibodies coat pathogens ➔ targets them for destruction

Question 7

overall immune response

Answer 7

leukocytes sense antigen
↓
neutrophils, monocytes, macrophages, & dendritic cells get activated
↓
cause inflammation
↓
go to peyer’s patches (2º lymphoid org) where lymphocytes live
↓
dendritic cells & macrophages (APCs) activate T cells
↓
helper T cells activate B cells
↓
multiply & start making antibodies

• T cells & antibodies enter circulation & go to infx site ➔ know where to go b/c of inflammation
• changes in capillaries/surrounding cells that direct newly made antibodies to site to bind to pathogen & eliminate

Question 8

self-regulation

Answer 8

• immune sys recognizes infx is controlled & stops attack
• regulatory T cells suppress inflammation
• T & B cells form memory so antibodies can mount rapid response next time ➞ lasting immunity

Question 9

passive immunity

Answer 9

• across placenta
• colostrum = first milk dam makes ➞ high in maternal antibodies that are absorbed into bloodstream before gut closure (< 48h postpartum)
  
  • in ruminants
  • very short-term
  • jxns in villi not yet formed
  • antibodies = big mol ➞ cannot pass through villi
• mature milk contains antibodies & antimicrobials
  
  • act on microbes at epithelial surfaces
  • protects against respiratory & GI infx
  • works as long as milk is being consumed
  • get antibodies from mother they cannot yet make themselves

Question 10

anatomical & physical barriers for the immune system

Answer 10

• skin
  
  • mucus
  • peristalsis
  • flushing (tears, saliva, urine)
  • cilia of GIT

Question 11

chemical barriers of the immune system

Answer 11

• acidic pH (stomach, vagina)
• sweat
• bile salts
• digestive enzymes
• non-specific IgA
• antimicrobial peptides
  
  • paneth cells in crypts make defensins & cryptdins ➞ enzymes disrupt bacterial membranes & metabolize to prevent from growing
  • lysozyme in tears & saliva breaks bonds in cell wall of bacteria ➞ cleavage makes cell walls leaky
• microbial: competition for space & nutrients (commensal)

Question 12

PAMPs

Answer 12

pathogen associated molecular patterns

• common cell-surface antigens on pathogens that help cells of innate immunity recognize as non-self
  
  • ex: lipopolysaccharides

Question 13

PRRs

Answer 13

pattern recognition receptors on epithelial cells/APCs that recognize & bind to PAMPs

• triggers inflammatory response: series of changes at infx site (point of pathogen contact)
• produce cytokines: immune regulators that affect nearly cells & cause inflammation

Question 14

cytokines

Answer 14

immune regulators that affect nearly cells & cause inflammation

Question 15

innate immunity pathway

Answer 15

• pathogens have common cell-surface antigens: pathogen associated molecular patterns (PAMPs)
  
  • ex: lipopolysaccharides
• pattern recognition receptors (PRRs) on epithelial cells/APCs recognize & bind to PAMPs ➞ triggers inflammatory response: series of changes at infx site (point of pathogen contact)
• produce cytokines: immune regulators that affect nearly cells & cause inflammation
• inflammation begins on contact