Chapter 15 Lymphatic system and Immunity

Question 1

What is the lymphatic system?

Answer 1

• Critical for circulatory system function and immune system
  
  • Fluid recovery (maintain blood pressure)
  • Site of immune cells (disease fighting cells)

Question 2

What are two parts of the lymbic system?

Answer 2

• Two parts:
  
  • Network of vessels that extends to all tissues of the body
  • Organs and tissues that produce and maintain immune cells
    
    • Organs and tissues include:
      Lymph vessels/nodes, tonsils, thymus, spleen, bone marrow

Question 3

Why is there fluid recovery?

Answer 3

• Capillaries are “leaky”
  
  • 2-4 liters of water diffuse into tissues daily
  • Called interstitial fluid
• Lymph vessels absorbs interstitial fluid
• Transport back to blood vessel

Question 4

How many liters of blood do humans hold?

Answer 4

Humans  4-6 liters of blood

Question 5

What is Elephantiasis?

Answer 5

• A parasite infects lymphs vessels and prevents reabsorption of lymph fluid
• Leads to edema in limbs and over time the skin stretches and thickens (testicles and breasts can also be affected)

Question 6

What are lymph nodes and how are they related to immunity?

Answer 6

• Interstitial fluid is filtered by lymph nodes for pathogens
• Bean-shaped structures of lymph tissue
  
  • Contain lymphocytes that help with immunity
  • Lymphocytes are a subset of white blood cells
• When sick, lymph nodes become swollen and painful
• This occurs because the body is issuing an immune response

Question 7

How is resistance organized?

Answer 7

• Pathogens are disease causing organisms
  
  • Bacteria, viruses, parasites, fungi
• Body has two mechanisms to deal with pathogens:
• Nonspecific Immunity(attack any foreign invaders):
  
  1. External Barriers
  2. Phagocytic Cells
  3. Immunological Surveillance
  4. Complement System
• Specific Immunity(attack a SPECIFIC foreign invader):
  
  1. Cell-mediated resistance
  2. Antibody-mediated resistance

Question 8

How is resistance organized?

Answer 8

Creates a “layered” approach to protection

Question 9

What are white blood cells also known as and what are they?

Answer 9

• White blood cells are known as leukocytes
• Also produced in red bone marrow
• Only about 5,000-10,000 cells per drop of blood
• Retain organelles
• Cells of immunity
  
  • Two subsets based on original stem cell
  • Neutrophils, monocytes, macrophages basophils, eosinophils  ~70% of white blood cells
  • Lymphocytes (B and T cells, natural killer cells)  ~30%

Question 10

Which of the following is an example of a non-specific defense?

A. Antibodies causes agglutination
B. Cells searching for a pathogen with a known antigen
C. The mucous membrane of your nose

Question 11

What are the three nonspecific resistances?

Answer 11

1. External barriers
   
   • Integumentary system (skin): dryness, acidity
   • Mucous membranes: “traps” pathogens
2. Phagocytic cells
   
   • Remove pathogen by engulfing them
3. Immunological Surveillance
   
   • Natural killer cells
   • Recognizes any abnormal antigens
   • Recognitions results in destruction of the pathogen OR infected cell by lysis

Question 12

What is a result of nonspecific resistance?

Answer 12

FEVER

• Increase in body temperature
• Caused by pyrogens
  
  • Proteins released by macrophages during phagocytosis
  • Results in hypothalamus “resetting” body’s thermostat
    
    • Aspirin or ibuprofen prevents pyrogens from delivering message to brain
• Increases metabolism
• Fevers are a natural response to infection…may be beneficial!

Question 13

Lymphocytes play a direct role in non-specific immunity.

A. True
B. False

Question 14

What does specific Resistance equal?

Answer 14

IMMUNITY

• Resistance directed towards a specific pathogen
  
  • Body also develops “memory” of pathogen for future protection

Question 15

What are the two types of immunity?

Answer 15

Two types of immunity

• Cell-mediated immunity  infected cells/pathogens are killed by specific T-cells
• Antibody-mediated immunity  infected cells/pathogens are killed by antibodies produced by B-cells
• Two systems are coordinated by Helper T-cells

Question 16

What happens at step one?

Answer 16

Step 1 – Antigen Presentation

• First step  Antigen Presenting Cells (APC’s)
  
  • Protein complex on surface “presents” antigens to T cells
  • Class I MHC – all nucleated cells in your body
    
    • “HELP – I’M INFECTED!!! KILL ME!!!”
  • Class II MHC – macrophages, B cells
    
    • “WARNING – HERE’S A BAD ANTIGEN. FIND AND DESTROY!!!”

Question 17

What activates at step 2?

Answer 17

• This step is required for cell-mediated, antibody-mediated and non-specific immunity
• Start with inactive Th cells
  
  • Protein complex on surface specific to antigen (T cell receptor)
• Activation
  
  • Naïve Th cell binds APC antigen on class II APCs (macrophage or B cell)
    
    • Utilizes CD4 protein and Th receptor on Th cell membrane

Question 18

What is activated in step two and what does it do to the memory? (Part two)

Answer 18

• Activated Th cells secrete cytokines
  
  • Cytokines help stimulate Tc cell and B cell activation
  • Help stimulate non-specific responses
  • Integrate cell-mediated, antibody-mediated immunity and non-specific
• Activation also causes differentiation of memory Th cells
  
  • Faster response than naïve cells with next encounter of same antigen

Question 19

What is activated at step three?

Answer 19

Step 3 – Activation ofCytotoxic T cells (Tc)

• Initiates cell-mediated immunity  cells killing infected cells
• Start with inactivated Tc cell
  
  • Protein complex on surface specific to antigen
• Activation – “Two-Signal Model”
  
  • Naïve Tc cell binds APC antigen from class I APCs (infected cells)
    
    • Utilizes CD8 protein and Tc receptor on Tc cell membrane

Question 20

What do the Tc cells of step three do and what do they do to memories?

Answer 20

• Activated Tc cells directly attack infected cells (class I) with same presented antigen
  
  • Results in lysis
• Activation also causes differentiation of memory Tc cells
  
  • Faster response than naïve cells with next encounter of same antigen

Question 21

What type of cells use a CD8 protein to bind a presented antigen?

A. Helper T cells
B. Natural Killer cells
C. Cytotoxic T cells
D. Macrophages

Answer 21

C. Cytotoxic T cells

Question 22

Overview of T-Cell Activation

Answer 22

Question 23

What is activated at step 4?

Answer 23

Step 4 – B-Cell Activation

• B cells have antibodies for specific antigens on cell surface
• Sensitization  Antigen binds antibody, engulfs antigen, presents antigen
• Activation  Bind Th cell activated with same antigen, “Co-stimulation”
  
  • This is a required step to prevent an accidental activation
• Produce plasma cells  make and secrete antibodies
• Produce memory B cells  faster response if exposed to antigen again

Question 24

How do antibodies work?

Answer 24

• Plasma cells produce about 2000 antibody molecules per second over 4-5 days
• It is predicted that the body can produce 10 billion different types of antibodies
• Antibodies have several modes of actions
  
  • Neutralization  bind to part of antigen that is toxic
  • Agglutination  antibodies bind to multiple antigens causing them to stick together and prevents transport throughout body
  • Improved phagocytosis due to presence of bound antibodies

Question 25

Activated Helper T cells are required for both the cellular and antibody immune responses. ## Footnote A. True B. False

Question 26

What is specific resistance?

Answer 26

* Specific response occurs in lymph nodes * That’s why nodes get swollen when you are sick * Immunity creates a memory of disease * Quick response if presented with same antigen * Memory T and B cells * Both the cellular and the antibody response * Vaccines are weakened forms of a disease * They cause the immune response at a low rate, so low you normally do not get sick * T and B memory cells are produced so if faced with the same disease your immune system launches a fast attack