15: Humoral Immunity

Question 1

Follicular vs marginal B cells

Answer 1

Follicular: recirculating (majority)
Marginal: in spleen for blood-borne Ags

Question 2

What causes B cells to undergo anergy

Answer 2

B cell recognizing Ag without BCR cross linking, co-stimulatory ligands, or cytokine support

Question 3

What is critical for class switching and affinity maturation to occur?

Answer 3

CD40-CD40L interaction

Question 4

Where do affinity maturation and class switching occur?

Answer 4

GCs

Question 5

Class switching process: 2 steps

Answer 5

1. Th and Tfh cell cytokines open switch regions in heavy chain DNA
2. VDJ gene segment recombined with downstream C region gene

Question 6

Affinity maturation

Answer 6

AID introduces point mutations in switch regions of variable and light Ig genes -> high affinity Abs

Question 7

High affinity selection checkpoint after affinity maturation

Answer 7

FDCs provide Ags to new BCR receptor to sample -> if higher affinity, B cell clone is selected for further differentiation

Question 8

Where are long lived plasma cells found?

Answer 8

Bone marrow (IgG), mucosa (IgA)

Question 9

Plasma cells: what cell marker increases

Answer 9

CD27

Question 10

Anti-apoptotic marker on memory B cells

Answer 10

Bcl-2

Question 11

What cytokine signal is required to keep memory B cells alive?

Answer 11

IL-7

Question 12

Antibody feedback

Answer 12

Excess Abs bound to a pathogen will block further Ab production

Question 13

Microbe neutralization: classes and purpose

Answer 13

Done by all Ig classes, neutralizes the infectivity of a pathogen + block pathogens from binding cell surfaces to gain entry

Question 14

Which Ig is a super efficient complement fixer?

Answer 14

IgM

Question 15

Waste management function of Abs

Answer 15

Opsonization -> clearance of ICs from circulation in a non-inflammatory manner

Question 16

How RBCs play a role in waste management

Answer 16

CR1 on erythrocytes bind circulating ICs -> liver/spleen -> removal of ICs and digestion by phagocytes -> RBCs continue to circulate

Question 17

ADCC: four cell types that perform it

Answer 17

NK cells, macrophages, neutrophils, eosinophils

Question 18

ADCC

Answer 18

IgG or IgE bind surface-bound Ag -> NK cell binds Ab via Fc receptor and kill via lytic enzymes, TNF, and perforin/granzymes

Question 19

What class does Th2 cytokines influence class switch to?

Answer 19

IgE

Question 20

Cells that produce natural Abs against blood group Ags

Answer 20

B1 cells, marginal zone B cells

Question 21

FcRN

Answer 21

Neonatal IgG receptor for recycling and transcytosis of IgG across placenta

Question 22

How maternal IgG crosses placenta

Answer 22

IgG pinocytosed from circulation -> bound to FcRN in endosome -> translocates to fetal circulation and releases when at neutral pH

Question 23

Most vulnerable period for an infant’s immune system

Answer 23

6-12 months

Question 24

Passive immunization

Answer 24

Introduction of Abs or antiserum into a naive recipient

Question 25

Difference between passive and active immunization

Answer 25

Passive: immediate, no memory Active: lag time, makes memory

Question 26

Functions of passive immunization

Answer 26

1. Prevent disease after known exposure 2. Ameliorate sx of ongoing disease 3. Protect immunosuppressed pts 4. Block bacterial toxins

Question 27

IVIG uses

Answer 27

Treatment of some autoimmune and inflammatory diseases

Question 28

Monoclonal Abs

Answer 28

Highly specific epitope recognition -> stimulates a variety of immune responses -> come with side affects

Question 29

Uses of monoclonal Abs

Answer 29

Cancers, autoimmune diseases