lecture 32

Question 1

how did we fight covid

Answer 1

body produces antibodies - counters viruses

Question 2

why did people get infected with omicron if they already have covid antibodies

Answer 2

omicron = variant
mutations change aa sequence of areas that covid antibody binds to = diff now
so antibodies wont work

Question 3

define antigen

Answer 3

any molecule - usually a protein that elicits an immune response

Question 4

define antibody

Answer 4

iggs
proteins - present in blood and other body fluids
bind to antigens and marks them for destruction by phagocytic cells
tags as antigen to be removed

Question 5

define autoimmune disease

Answer 5

immune reaction against its own antigens (proteins)
immune system must be able to distinguish between self and non self

Question 6

what is adaptive immune response

Answer 6

antigen specific immune response
humoral and cellular immunity

Question 7

define humoral immunity

Answer 7

production and secretion of antibodies by specialized lymphocytes - white cells = called b cells

Question 8

define cellular immunity

Answer 8

Specialized lymphocytes called t cells produce t cell receptors that recognize and bind antigens found only on the surface of bodies own cells
eliminates cells that express foreign antigens

Question 9

describe hematopoietic tree

Answer 9

Hematopoietic stem cell in bone marrow = makes all cells - differentiates and matures

Question 10

what cells are adaptive vs innate immunity

Answer 10

adaptive immunity = antigen specific defence = t cell, b cell, nk cell
innate immunity = non specific defense but quick response = neutrophil, basophil, eosinophil, macrophage

Question 11

describe development of humoral - b cell - and cellular - t cell - immunity

Answer 11

Lymphocytes = from stem cells
b cells mature in bone marrow
t cells mature in thymus
they recognize foreign antigen then differentiate and mature (b cells to plasma cells and t cells = attack)
autoreactive b and t cells are eliminated during development

Question 12

what can each B and T cell recognize

Answer 12

a unique non self antigen that can elicit immune response
Diversity in antibody and t cell receptor - do not know what we will be exposed to

Question 13

describe clonal selection of b cells

Answer 13

large pool b lymphocytes - each is specific for ONE antigen
antigen binds then b cell divides

Question 14

describe clonal expansion of selected b cell

Answer 14

clone of b cell = specific for same antigen
Proliferation of lymphocytes = primary immune response
then plasma cell and secrets antigens

Question 15

describe secondary response

Answer 15

by memory b cells that have been activated
if second expose = antigen binds memory cells
rapidly gives rise to secondary immune response = faster

Question 16

what happens for t cells - clonal selection and secondary response

Answer 16

similar processes as b cell for t cell and t cell receptor

Question 17

why do vaccines work

Answer 17

secondary immune response

Question 18

describe vaccines- active agent

Answer 18

antigen of vaccine = makes primary immune response
intact but inactivated - non infective pathogen
Attenuated - reduced infectivity forms of pathogen
purified components of pathogen that have been found to be highly immunogenic
generates memory cells so body is ready when second infection happens

Question 19

describe conventional methods vs next gen vaccines

Answer 19

conventional methods - culturing virus = takes long time
next gen vaccines = such as rna vaccines use host cells to produce antigen = much faster, put rna in body = antigen not produced outside body

Question 20

what are immunoglobulins - explains

Answer 20

proteins that protect us
2 identical light chains
2 identical heavy chains
y shaped
heavy chains have additional diversity region
light chains have variable, joining and constant region, aa sequences here recognize specific antigens

Question 21

describe light chains

Answer 21

2 types = kappa and lamda - 2 locus
encoded on diff chromosomes
Segments = v, j and c
kappa/kappa or lamda/lamda - not mix

Question 22

describe heavy chains

Answer 22

five types - depends on aa sequence of constant region - alpha, delta, gamma, epsilon or mu
Segments = v, d, j and c
each type of light chain can potentially combine with each time of heavy chain

Question 23

how many protein coding genes does human genome have

Answer 23

20 000 - 25 000

Question 24

how many antibodies can humans produce

Answer 24

10^11 antibodies with diff specificities

Question 25

name 3 ways that generate antibody diversity

Answer 25

somatic recombination
junctional diversity
somatic hypermutation

Question 26

what do b cells produce - antibodies

Answer 26

Unique light and heavy chain combos that can recognize a specific antigen

Question 27

describe somatic recombination of kappa light chain

Answer 27

between v and j segments
one v and one j = spliced together - intron removed and everything downstream of v and upstream of j segment
produces dna found in mature b cell
does not happen in germ line dna but b cell dna

Question 28

how are v and j segements spliced together

Answer 28

rag1 rag2 and dna repair enzymes introduce ds dna breaks and join random v and j segements = occurs at level of dna
then transcription initiated by joining - 5’ to v segment
wont ever go back

Question 29

what happens to pre-mrna - splicing

Answer 29

spliced to produce unique combo of v-j-c light chain
mature mrna only contains one v, j and c segment = translated to functional light chain = ligated

Question 30

T or F = the immunoglobulin generated in a given b cell will NEVER be the same

Answer 30

FALLLLSEEE
will always be the same

Question 31

what do heavy chains have

Answer 31

locus has multiple D - diversity gene segments in addition to v, j and c segments

Question 32

describe math of antibody diversity

Answer 32

kappa = V - 30 and J - 5 = 150
lamda = V - 35 and J - 7 = 245
heavy chain = V - 100 and D - 23 and J - 5 and constant region - 5* = 100x23x5 = 11500

kappa x heavy = 1.7 mil
lamda x heavy = 2.8 mil
total = 4.5 mil

• while v d and j segments contribute to antibody specificity, constant regions of heavy chains dont

Question 33

describe junctional diversity

Answer 33

imprecise junction
few nts are lost or gained
can cause frameshift = produced nonfunctional gene if 3 codons eliminated
also indels

Question 34

describe somatic hypermutation

Answer 34

iggs subject to high mutation rate
deamination of cytosine –> becomes uracil
uracil is replaced by the dna repair mechanisms by another base = causes point mutation
changes aa sequence that recognizes antigen

Question 35

what are t cell receptors composed of

Answer 35

alpha and beta chains that have variable regions
= membrane bound proteins expressed at surface

Question 36

describe alpha chain - t cell receptors

Answer 36

44-46 v gene segments
50 j gene segments
single c segment

Question 37

describe beta chain - t cell receptors

Answer 37

Similar to alpha chain but contains d gene segments

Question 38

describe t cell receptor diversity- how

Answer 38

somatic recombination
junctional diversity
BUT NO HYPERMUTATION