Adaptive humoral immunity

Question 1

is humoral immunity - adpative or innate?

Answer 1

Both!

innate- complement and cytokines

adpatice- antibody meidated specific immunity

protects agaisnt extracellular pathogens

Question 2

what are BCRs

Answer 2

B cell recpeotrs- antibodies imbedde in there surface

plasma cells (B cells) secrete Antibodies whicha re a soluble form of BCR

Neutralisation, Opsonisation, complement activation

Question 3

describe tbhe structure of antibodiees

Answer 3

light chain- one variable , one cosntant

heavy chain- one variable , multipe cosnatynt doamins (3 or 4)

2 identical light chians, 2 indeictla heavy gains

Varaibl;e region- Fab ragements

constnac- Fc grfament

Question 4

what is the function of the Hinge region?

Answer 4

allows movement and therefore greater interactions with epitopes ( these are sites on antigen recognised by immune system)

Question 5

describe the light chain of an Ig

Answer 5

1 variable and 1 contanrt domain

domain can either be K (kappa) or λ (lambda)

but same within one Ig

Question 7

what are the 5 classes of immunogobluins - heavy chain determines the class

Answer 7

igM

IgD

IgG

IGA

IGE

Question 8

Labell the following

Answer 8

Question 9

name the hevay change for each of the immunoglobulin classses

Answer 9

γ (gamma; IgG)

α (alpha; IgA)

μ (mu; IgM)

ε (epsilon; IgE)

δ (delta; IgD)

Question 10

which Igs have 3 constant regions and which have 4 and nohinge regions?

Answer 10

igG, igA, and IgD have 3 constant domains with hinge regions

igM and igE have 4 cosnatnt regions but no hinge region

Question 11

which ig is secrted as a dimer

Answer 11

igA (also as a monomer)

Question 12

which ig exists as a pentamer

Answer 12

igM

Question 13

describe the role of IgG

Answer 13

4 subclasses (igG1-4)

named in there decreasing abudnance in serum

main coruclaotry ig fro secodnary immune response

can cross placenta- not found in secretions

Question 14

describe igA

Answer 14

found in2 subclasses igA2 and IgA2

found in blood but also acts in defence of mucosal surfaces

secreted into gut and repsiroatyr and milk

cannot cross the placenta, bind to macrophages or mast cell receptors

J chain- dimer

Question 15

describe igM

Answer 15

hgih mocleulcar weight

pentamer

due to size normally present in blood not tissues

main Ig in primary response

monomeric form- niave B cell surfacve

Question 16

describe function of IgD

Answer 16

exists on surface of B cells (membrane cound)

BCR

first antivbodies to react to a new antigen before class switching

function unkwon

Question 17

Describe IgE

Answer 17

invovled in defence agaisnt multicellular paraiste

allergic diseas-e asrthma

Question 18

how do phagocytes bind to opsonised pathognes

Answer 18

phagocytes hae antibody Fc receptors-

Question 19

what is VDJ and VJ random combination do?

Answer 19

we have multiple versions of variabel diveristy and joining gene segments

hevay chain- CDJ segements

ligh chain- VJ segments

used to geenrate diversity

Question 20

what is the function of RAG?

Answer 20

recombination activign gene protein

binds th a random v segment and random segment and binds themtogether- pinches off the loop

induces a doubel stranded break in DNA

DJ recombination

RAG then binds to random V and new DJ section. - form another loop , Ds tbreak- DNA then repaied

VDJ reocmination- 10 million variabel combinations

this is repeasted for light chain but onyl chaisn V and J

Question 21

how is diveristy during VDJ increased form 10 million (RAG)—-> 100 billion

Answer 21

Tdt ( terminal deoxynucleotidyl transferase)

joins the VDJ messily

adding extra DNa bases- vriaable region differenet every time

Ds repair protein

Question 22

what sydnrome kis caused by a mutation ins RAG

Answer 22

SCID- severe combine dimmunodeificneyc syndrome

Question 23

where does CDJ reocmibation occur?

Answer 23

Ig light (VJ) heavy (CDJ)

TCR alpha (DJ) and beta (VDJ)

Question 24

what is B cell tolerance

Answer 24

B cells exposed to antigens in the bone marrow - to see if they react tos elf antigens

if they react can reaarnagelight chain- receptor editing

25% do this- if they are still reactive theu are destpryed

Question 25

if B cells are only exposed to antigens found in the bone marrow how do they have tolerance to antigens in the rest of the body?

Answer 25

broaldy antigens in bone marrow are the same as the antigne sene in lymhpatic tisse because B cells are niaev onyl cirulate in lymphatic tissues then they shouldt react to any body tissues if a B cell does encounter self antigen, peripherl mechanisms turn it off- Anergy

Question 26

Describe B cell activation

Answer 26

B cells can recognise Antigens presenting by APC MHC type 2 but alos recognise antigens floating in the bodily fluids as they get tagged by complement travel to in B area, lymphoid follciles- contaisn follicular dendiit cells tha display antigens to B cells

Question 27

Describe the Germinal Centre in B cell activation

Answer 27

folliculaer denritic cell uptkaen ciruclating antigen- presnts B cell engulfs the antigen and presents meanwhoile a T cell has also be acivtaed by APC dendiritc cell in the mollcile this T cell will meet its matching B cell presenting antigen. B cell proliferates and replicates Lymphoid follicke B cell rpaid prolifermaintion become germinal centres this proliferation causes lymph nodes to swell during infection

Question 28

describe the proccces that occur after B cell Activation by T cell in the germinal centre?

Answer 28

* somatic hypemutation- replication of B cell imperfect * small errors in BCr- to get better fit to antigen * best fit gets selected- Affifnity mautration * B cell may do this many times * Release of B cells * Memeory B cells * Palasma B cells * also get Isotype class switching at same time as somatic hypemrutation

Question 29

describe isotype class switching

Answer 29

occurs at the same time as somatic hypermutation invovles swithcingthe FC constant region in begiing typically IgM and soem IgD- can change to bets deal with infection at hand cytokines help detemrine class swithcing

Question 30

which 4 processes generate antibody diversity

Answer 30

combinatorial diveristy (VDJ) junctional diveristy affinity maturation class switching

Question 31

what are C exons

Answer 31

C- exons encode constanrt regions hevay chain C gene segment are cluster of econs, encodes domains or a hinge region different types determine class of antifodies Cμ - IgM Cδ- IgD Cγ3, C γ1,Cγ2, Cγ4, - IgG Cε - IgE C α1,C α2- IgA

Question 32

what is junctional diverity

Answer 32

formation of junctions between geen segemtns- nucleotides can be added or removed junctional felxivbility- sligh variation in psotions of segm,ental joining when exons are spliced Nucleotide addition- can be added by Tdt( terminal deoxynucleotidyl tranferase) nucloetide deletion- in combination with combinatroal and junctional diverity- 100 biullion different BCR receptros non functional in 2/3 - these b cells progenitors will nerv mature to B cells- maturity at the csot of many

Question 33

what is affinity maturation/ somatic hypermutation? what is AID

Answer 33

process of making antibody a better fit for its antigen when active B cells replicate they increase in number- express **AID ( activation induced cytidine deaminase)-** creates mutations in variable domain (VDJ)- **somatic hypermutation** mutatiosn tightly regulateed Ig wtih higher affinity as passively selected for

Question 34

describe class swtichig? which enzyme is involved (hint same as enzyme involed in soamtic hypermutation)

Answer 34

first Ig BCr produced in naive B cell is IgM or IgD differen calls of Ig have differen protperites better at differen functions a single B cell cna produce different classes of Ig specific to same antigne before each **heavy chain C gene segment** there is a DNa sequency called a s**witch site** ( locus of class swithcing -rearrnagement occurs) Activated By **AID**