Immunity overview

Question 1

Contrast passive and active immunity

Answer 1

Passive

• receiving preformed Ab (e.g. breastfeeding)
• rapid protection
• short duration (Ab half life= 3 weeks)

Active

• exposure to a foreign antigen (e.g. flu shot)
• slow protection
• long duration -> memory lymphocytes

Question 2

Define immunogen

Answer 2

A molecule that induces an immune response

Question 3

Define antigen

Answer 3

A molecule that binds to (is recognized by) adaptive immune mediators aka lymphocytes

Question 4

Define tolerogen

Answer 4

A molecule that induces immune unresponsiveness to subsequent doses of that molecule (STILL recognized by immune system, just ignored)

Question 5

Describe characteristics of a very immunogenic molecule

Answer 5

Large and complex, intermediate dose, administered SubQ, adjuvant (bacteria), and effective interaction with MHC complex

Question 6

What is the difference in specificity between innate and adaptive immunity?

Answer 6

Innate system uses pattern-recognition receptors (TLRs, complement proteins) to recognize PAMPs *limited diversity

Adaptive system uses antien receptors (TCRs recognize peptides, BCRs recognize large complexes of carbs/fats/protein/etc)

Question 7

Which immune response is most effective long term?

Answer 7

Adaptive immunity (memory T and B cells)

Question 8

What are the key immunologic decision points?

Answer 8

1. Self or foreign?
2. Nature of invading antigen/microbe (intracellular/extracellular?)
3. Timing of exposure (primary or secondary immune response?)

Question 9

Contrast live attenuated and inactivated vaccines

Answer 9

Live attenuated

• Modified to decrease pathogenicity (limited growth after injection) *may revert to virulent form
• Induces cellular response (T cells)
• Strong, life-long immunity

Inactivated

• Heat or chemically inactivated pathogen (retains epitope on surface) *stable and safer than live
• Induces humoral response (B cells)
• Weaker immunity- requires booster vaccine

Question 10

What are generative and peripheral immune organs?

Answer 10

Generative= bone marrow and thymus

Peripheral= lymph nodes, spleen, GALT, tonsils, etc

Question 11

What are the main components of innate immunity?

Answer 11

Epithelial barriers, phagocytic leukocytes (macrophages, neutrophils), DCs, NK cells, complement

**always “on” so get immediate response

Question 12

How is the innate immune system activated?

Answer 12

Pattern recognition receptors (e.g. TLRs) recognize PAMPs on bacteria, virus, fungal, or parasite pathogens and activate proinflammatory/anti-viral signaling pathways

**NO MEMORY

Question 13

How is the adaptive immune system activated?

Answer 13

1. Antigen (specifically the epitope region) binds to Ab or T cell receptor
   **TCRs only recognize peptide fragments in MHC I/II
2. MHC I complex -> activates CD8/cytotoxic T cells
   MHC II complex -> activates CD4/helper T cells
3. CD8 T cells KILL
4. CD4 T cells HELP
   
   1. Release cytokines
   2. CD40L on T cell binds CD40 and activates cells of innate immunity (macrophage/DC) or naive B cells

Question 14

Which adaptive immune response deals with intracellular pathogens? Extracellular?

Answer 14

T cells respond to intracellular pathogens (cytoplasmic on MHC I, vesicular/phagocytosed on MHC II)

B cells respond to extracellular pathogens *“Immune surveillance” with circulating Abs

Question 15

What are the antibody isotopes?

Answer 15

IgD (only on naive B cells), IgM (T cell independent), IgE, IgG, and IgA

Question 16

What is the function of dendritic cells?

Answer 16

Present antigens on MHC I/II to T cells in the peripheral lymph tissues

Question 17

What infection is characterized by high eosinophil levels?

Answer 17

Parasitic (or allergic response)

Question 18

What infection is characterized by high neutrophil levels?

Answer 18

Bacterial

Question 19

What infection is characterized by high lymphocyte levels?

Answer 19

Viral

Question 20

What marker is common for all T cells?

Answer 20

CD3+

Question 21

What markers are used to differentiate between different types of T cells?

Answer 21

CD4+ for helper T cells, CD8+ for cytotoxic T cells, CD4+/CD25+ for regulatory T cells

Question 22

What markers are used to identify B cells?

Answer 22

CD19/CD21 and FcR

Question 23

What markers are used to identify NK cells?

Answer 23

FcRgamma