Lecture 30 Flashcards
what part of the omicron spike protein is mutated to evade the immune system?
N-terminal domain and receptor-binding domain
hematopoietic tree
starting in BM, immune cells derive from hematopoeitic stem cell
then split into common lymphoid progenitor (adaptive) or common myeloid progenitor (innate)
humoral vs cellular immunity
humoral = B cells producing Ab
cellular = T cells bind Ag
development of humoral immunity
- lymphocytes originate from stem cells in BM
- B cells mature in BM
- B cells encounter Ag and mature into plasma cells that make Ab
development of cellular immunity
- lymphocytes originate from stem cells in BM
- T cells mature in thymus and enter circulation
- T cells use TCR to fight infection
clonal selection of B cell
B cell binds its antigen to cause B cell division
clonal expansion of selected B cell
B cell division = proliferation –> primary immune response
creates 1st wave: Ab-secreting plasma cells and memory cells that stay in circulation
2nd wave: if antigen encountered again
3 types of active agents of a vaccine
- inactivated
- attenuated
- purified components of pathogen
what does a successful vaccine rely on? why?
memory!
vaccine induces the primary immune response and generates memory cells that are active when the infection occurs
why are next generation vaccines better?
ex. RNA vaccine –> uses host cells to produce antigen which is much faster
how many types of light chains are there? what are they?
2: kappa and lambda
gene segments of light chains
V, J, and C
2 possible light chains
kappa/kappa OR lambda/lambda
how many types of heavy chains are there? what are they?
5: alpha, delta, gamma, epsilon, or mu
gene segments of heavy chains
V, D, J, and C
how many Ab can be produced with different specificities?
10^11
3 ways of generating Ab diversity?
- somatic recombination
- junctional diversity
- somatic hypermutation
describe somatic recombination of light chain (DNA –> pre-mRNA –> mature mRNA)
- RAG1/2 cuts at 3’ end of a variable region and 5’ end of a joining region to join random V and J segments (at level of DNA)
- transcription begins at the selected V region to make pre-mRNA with joint V and J and other J regions
- pre-mRNA is spliced to remove remaining J regions and mature mRNA with only 1 V, J, and C region is transplated
does a B cell always make the same Ab? why?
yes
because somatic recombination occurs at the DNA level
how much of Ab diversity is due to somatic recombination?
4.5x10^6
which Ab segment does NOT contribute to Ab specificity?
constant region
what is junctional diversity?
a few random nucleotides are lost or gained (may lead to frameshift that produces nonfunctional gene)
what is somatic hypermutation?
immunoglobulin genes have high mutation rate
example of point mutation created in somatic hypermutation
cytosine deaminated to uracil –> DNA repair mechanisms replace the uracil with another base to make a point mutation
2 chains of TCR?
- alpha
- beta
what gene segments are in the alpha chain?
V, J, C
what gene segments are in the beta chain?
V, J, D, C
what are the mechanisms for generating TCR diversity?
somatic recombination and junction diversity
