(I) Lecture 9: B cell Immunity Part II

Question 1

Primary functions of mature B-cells

Answer 1

• detect pathogens/potentially harmful antigens
• differentiate into plasma cells that secrete antibodies
• create memory

Question 2

How is B cell specificity changed?

Answer 2

Can ONLY change specificity of a B cell through gene rearrangement as a naive B cell

Question 3

Does class-switching change specificity? Somatic hypermutations?

Answer 3

NO, neither change specificity

Question 4

What antibody can be made without class-switching and hypermutations?

Answer 4

IgM

Question 5

IgM

Answer 5

• FIRST class produced by B cells (primary response)
• low affinity antibodies as monomers
• 10 binding sites as pentamers
• mainly found in blood and lymph
• can bind to different pathogens in planar or staple conformation
• C1q binds to IgM to start complement cascade

neutralizes circulating pathogens and activates complement

Question 6

IgG

Answer 6

• most ABUNDANT antibody class in serum
• LONG-lived
• includes different classes
• operates mainly in tissues

Question 7

IgA

Answer 7

• mainly present in SECRETION (MALT, saliva, mucus, tears, breast milk)
• found in LOW levels in circulation
• exists in monomer form but MAINLY in DIMERIC form in secretions
• not a potent opsonin

neutralizes pathogens and toxins

Question 8

IgE

Answer 8

• mainly known for roles in ALLERGY and ASTHMA
• made is SMALL quantities (has potent effects)
• activates mast cells that secrete histamines (proinflammatory cytokines)
• proposed role against parasites

Question 9

IgD

Answer 9

• minor immunoglobulin (only 0.2% of antigens)
• most IgD remains bound to naive and memory B cells
• main function: BIND ANTIGEN as BCR
• higher in secretions of UPPER RESPIRATORY TRACT

Question 10

When do adaptive immunity deficiencies typically show?

Answer 10

@ 9- 10 months old b/c that’s when adaptive immunity starts to kick in and they rely less on mother’s antibodies

Question 11

What antibodies are passed through natural passive immunity?

Answer 11

IgA

Question 12

Innate and Adaptive Immunity dynamics

Answer 12

1. establishment of infection
2. inductive phase (make cytokines)
3. effector phase (T cells + plasma cells make ANTIBODIES)
4. memory phase (all from adaptive immune cells)

Question 13

Stages of immune response

Answer 13

1. local infection and penetration of epithelium (immature DCs + macrophages eat pathogens and make cytokines)
2. local infection of tissues
3. lymphatic spread
4. adaptive immunity

Question 14

Antibody response

Answer 14

IgM kicks in earlier than IgG

IgG has higher levels in secondary response

Question 15

Antibody response during vaccination

Answer 15

Unimmunized donor (Primary response)
- IgM > IgG
- low affinity of antibody
- low somatic hypermutation

Immunized donor (Secondary response)
- IgG, IgA
- high affinity of antibody
- high somatic hypermutations

Question 16

Immunological memory and vaccines

Answer 16

Years after vaccine, the body is still making high levels of antibodies, especially IgG

making CD4 and CD8 memory cells as well but less than antibodies

Question 17

What immune components provide long term protection in vaccines?

Answer 17

• memory effector T cells (CTL, Th1, Tfh)
• memory B cells
• long-lived plasma cells (IgG, IgA, antibodies)

Question 18

Herd immunity

Answer 18

when a large portion of population becomes immune, it decreases spread
- provides protection to susceptible individuals (elderly, immunocompromised, unvaccinated)

ONLY achieved when a large percentage of population is immunized

Question 19

Main approaches to making a vaccine

Answer 19

• whole microbe
• sub-unit (parts that trigger immune system)
• next generation (just the genetic material)

Question 20

Whole microbe vaccines

Answer 20

• can use inactivated vaccine “killed” or live-attenuated vaccine “not as virulent”

Question 21

Live attenuated vaccines

Answer 21

Type of whole microbe vaccine
STRONG response

• microbe is made less infectious
• strategies are used to weaken pathogenicity of microbe w/o affecting its antigenic potential
• done through CELL CULTURING

Ex. MMR (mumps, measles, rubella), Polio, Yellow Fever

Question 22

Inactivated vaccines

Answer 22

Type of whole microbe vaccine
- weaker response

• pathogen is killed using HEAT or CHEMICALS
• must maintain its antigenic potential

Ex. cholera, hep A

Question 23

Subunits vaccines

Answer 23

SAFEST vaccine

• made of purified antigens/toxins
• microbes are grown in a lab and antigens are isolated and purified

Ex. DPT/Tdap

Question 24

Conjugate vaccines

Answer 24

Type of subunit vaccine

• polysaccharide antigens do not induce T-cell immunity
• B-cell response alone generates SHORT LASTING immunity
• polysaccharide antigen is conjugated w/ a protein vaccine to induce BOTH T-cell and B-cell immunity

Ex. meningococcal vaccine

Question 25

Next Gen vaccines

Answer 25

• uses “next gen” techniques like DNA manipulation and mRNA vaccines

Question 26

HPV vaccine

Answer 26

Human Papilloma Virus

L1 capsid protein self assembles into virus-like particles but contain no viral genetic materia
- empty on the inside

ZERO risk of infection

Question 27

What kind of vaccine is COVID vaccine?

Answer 27

mRNA vaccine

mRNA encodes spike protein of virus

Question 28

Correlation and Causation

Answer 28

Correlation does not mean causation

Ex. Just because MMR vaccine is typically given around time of autism diagnosis does NOT mean that it causes autism