Lecture 2B - Opsonization and Phagocytosis (Quan)

Question 1

What is opsonization?

Answer 1

attaching opsonins, such as IgG or complement fragments, to microbial surfaces to target the microbes for phagocytosis

Question 2

What are the primary opsonins?

Answer 2

IgG

Complement factor C3

Question 3

Where are Fc receptors found?

Answer 3

on phagocytes

Question 4

What does IgG first bind to?

Answer 4

microbes

Question 5

Where is a C3b receptor found?

Answer 5

on phagocytes

Question 6

Where is C3b found?

Answer 6

on microbe

Question 7

What are 2 receptors for opsonins?

Answer 7

1. Fc(gamma) on phagocytes
2. complement receptors on MAC
   
   • CR
   • leukocyte integrin Mac-1

Question 8

If an Fc receptor is named Fc(gamma) ___ ____, which antibody will it bind to?

Answer 8

IgG (G stands for gamma)

Question 9

If an Fc receptor is name Fc(alpha) __ __, which antibody will it bind to?

Answer 9

IgA (A stands for alpha)

Question 10

Fc receptors are named very specifically. For example, Fc(gamma)RI, Fc(gamma)RIIA,
Fc(gamma)RIIB, etc. Why?

Answer 10

The Fc is specific for your own cells, the (gamma/alpha/epsilon) says which antibody it will bind to (IgG, IgA, IgE), the R stands for “receptor” and the “Fab” region reacts with organism.

Question 11

What are the 3 classes of Fc(gamma) IgG receptors?

Answer 11

1. Fc(gamma) RI (CD64)
2. Fc(gamma) RII (CD32)
3. Fc(gamma) RIII (CD16)

Question 12

How do neutrophils signal that they are apoptotic?

Answer 12

Normal neutrophils have lots of CD16 Fc(gamma) RIII. When they lose this, they are “displaying death sign”, and macrophages begin to phagocytose the neutrophils.

Question 13

What is Fc(gamma) RII important for?

Answer 13

phagocytosis of IgG coated particles

Question 14

Which complement factors are chemotactic?

Answer 14

C3a and C5a

Question 15

Which two complements are mainly for opsonization?

Answer 15

C3b and C3bi

Question 16

What are the receptors on neutrophils?

Answer 16

1. LPS receptor
   
   • CD14
   • TLR4
2. CR3, 4
   
   • complement receptors (C3b)
3. Scavenger receptor
   
   • sialic acid-bearing protein
4. Mannose receptor
   
   • binds mannose
5. Glycan receptor
   
   • polysaccharides
6. TLRs

Question 17

What are the receptors on macrophages?

Answer 17

1. LPS for bacteria
2. TLR
3. Fc receptors for antibodies
4. complement receptors

Question 18

What factors increase PMN #s?

Answer 18

stress
injury
infection
increased cytokine levels

Question 19

What are the 2 primary mechanisms for destruction and killing?

Answer 19

1. oxidative (NO and ROS)

2. non-oxidative (enzymes, cytoplasmic granules, pH change)

Question 20

What are 5 kinds of phagocytic cells?

Answer 20

1. Neutrophils (PMNs)
2. Macrophage/Monocyte
3. Eosinophils
4. Basophils
5. Dendritic Cells

Question 21

How to pathogens try to avoid death?

Answer 21

1. Kill immune cells
2. inhibit tagging or inactivate phagocytosis
3. survive inside the macrophage