(I) Lecture 9: B cell Immunity Part II Flashcards
Primary functions of mature B-cells
- detect pathogens/potentially harmful antigens
- differentiate into plasma cells that secrete antibodies
- create memory
How is B cell specificity changed?
Can ONLY change specificity of a B cell through gene rearrangement as a naive B cell
Does class-switching change specificity? Somatic hypermutations?
NO, neither change specificity
What antibody can be made without class-switching and hypermutations?
IgM
IgM
- 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
IgG
- most ABUNDANT antibody class in serum
- LONG-lived
- includes different classes
- operates mainly in tissues
IgA
- 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
IgE
- 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
IgD
- 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
When do adaptive immunity deficiencies typically show?
@ 9- 10 months old b/c that’s when adaptive immunity starts to kick in and they rely less on mother’s antibodies
What antibodies are passed through natural passive immunity?
IgA
Innate and Adaptive Immunity dynamics
- establishment of infection
- inductive phase (make cytokines)
- effector phase (T cells + plasma cells make ANTIBODIES)
- memory phase (all from adaptive immune cells)
Stages of immune response
- local infection and penetration of epithelium (immature DCs + macrophages eat pathogens and make cytokines)
- local infection of tissues
- lymphatic spread
- adaptive immunity
Antibody response
IgM kicks in earlier than IgG
IgG has higher levels in secondary response
Antibody response during vaccination
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
Immunological memory and vaccines
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
What immune components provide long term protection in vaccines?
- memory effector T cells (CTL, Th1, Tfh)
- memory B cells
- long-lived plasma cells (IgG, IgA, antibodies)
Herd immunity
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
Main approaches to making a vaccine
- whole microbe
- sub-unit (parts that trigger immune system)
- next generation (just the genetic material)
Whole microbe vaccines
- can use inactivated vaccine “killed” or live-attenuated vaccine “not as virulent”
Live attenuated vaccines
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
Inactivated vaccines
Type of whole microbe vaccine
- weaker response
- pathogen is killed using HEAT or CHEMICALS
- must maintain its antigenic potential
Ex. cholera, hep A
Subunits vaccines
SAFEST vaccine
- made of purified antigens/toxins
- microbes are grown in a lab and antigens are isolated and purified
Ex. DPT/Tdap
Conjugate vaccines
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
Next Gen vaccines
- uses “next gen” techniques like DNA manipulation and mRNA vaccines
HPV vaccine
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
What kind of vaccine is COVID vaccine?
mRNA vaccine
mRNA encodes spike protein of virus
Correlation and Causation
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
