10) MHC Flashcards
3 main Ag recognition molecules in the immune system
- TCR
- sIg
- MHC
2 main functions of MHC in T-cell response
- establish library of T-cells during development
- activation of mature T cells
2 best known MHC molecules
- human (HLA)
- mouse (H2)
MHC similar to Ig
MHC I
divided into 3 independent loci (A, B, C)
MHC I
3 variable portions of MHC I
𝛼1
𝛼2
𝛼3
invariant portion of MHC I
β2 microglobulin
MHC I AA length
8-9
binds to β2 microglobulin of MHC I
CD8
each individual expresses —- MHC I molecules
6
(2 HLA-A, 2 HLA-B, and 2 HLA-C)
subdivided into DP and DR
coding region for MHC II
consists of parallel transmembrane 𝛼 and β chains
MHC II
MHC II AA length
12-25
binds to invariant β region of MHC II
CD4
MHC II always expressed on…
B cells
dendritics
thymic epithelials
can be induced to express MHC II
T-cells
macros
group of complement factors found in serum
MHC III
what kind of Ag does MHC II present?
exogenous
internalized by endocytosis or phagocytosis
what kind of Ag does MHC I present?
endogenous
synthesized within the cell
MHC — presents antigens found in vaccines with a non-infectious viral particle
II
parameters to consider when trying to elicit an immune response
- amount of Ag
- timing of exposure
- route of entry
immunogenicity depends on…
- complexity of Ag/more epitopes
- foreign
- large enough
added to enhance immunogenicity of vaxx
adjuvant
time before Ab is detectable in serum
latent phase
(1-2 weeks)
production and degradation of Ab reach equilibrium
steady state
anamnestic response
secondary response
differences in secondary phase
- lag phase shorter
- Ab production greater
- Ab production continues for longer
- more IgG than IgM
cell cooperation
Ab production requires cooperation between 2 lymph types
(irradiated mouse experiment)
irradiated mice with/without immune response
WITH:
- given spleen cells
- given BM + thymus cells
WITHOUT:
- given BM cells
- given thymus
main 2 roles of accessory cells (macros) in inducing immune response
- trap and concentrate Ag
- process and present Ag
NOT activated by free Ag
T -cells
process of Ag processing
- protein Ag enters cell (endo or phagocytosis)
- vacuoles merge with lysosomes, which have degradative enzymes
- peptides cut to 8-20 AAs
- immunodominant peptides lead to T-cell activation
T-cell receptor complex that requires CD4 to stabilize affinity
TCR-CD3
2 requirements for activation of T-cells
- engagement of receptors
- second signal (IL-1)
main cytokine serving as a second signal for T-cell activation
IL-1
happens first as T-cells are activated
- membrane phospholipids break down
- phosphorylation of intracellular proteins
- lymphokines secreted
cytokines involved in B-cell differentiation to active plasma cells
IL-4
IL-5
T-independent antigens
Ag capable of activating B-cells to product Ab in the absence of T helpers
properties of T-independent Ag
- large, polymeric
- multiple, repeating antigenic determinants
- generate primarily IgM
- do NOT give rise to memory
- macros seem to be required
