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xCase 17 SBA > Adaptive humoral immunity > Flashcards

Adaptive humoral immunity Flashcards

1
Q

is humoral immunity - adpative or innate?

A

Both!

innate- complement and cytokines

adpatice- antibody meidated specific immunity

protects agaisnt extracellular pathogens

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2
Q

what are BCRs

A

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

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3
Q

describe tbhe structure of antibodiees

A

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

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4
Q

what is the function of the Hinge region?

A

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

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5
Q

describe the light chain of an Ig

A

1 variable and 1 contanrt domain

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

but same within one Ig

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6
Q
A
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7
Q

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

A

igM

IgD

IgG

IGA

IGE

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8
Q

Labell the following

A
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9
Q

name the hevay change for each of the immunoglobulin classses

A

γ (gamma; IgG)

α (alpha; IgA)

μ (mu; IgM)

ε (epsilon; IgE)

δ (delta; IgD)

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10
Q

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

A

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

igM and igE have 4 cosnatnt regions but no hinge region

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11
Q

which ig is secrted as a dimer

A

igA (also as a monomer)

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12
Q

which ig exists as a pentamer

A

igM

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13
Q

describe the role of IgG

A

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

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14
Q

describe igA

A

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

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15
Q

describe igM

A

hgih mocleulcar weight

pentamer

due to size normally present in blood not tissues

main Ig in primary response

monomeric form- niave B cell surfacve

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16
Q

describe function of IgD

A

exists on surface of B cells (membrane cound)

BCR

first antivbodies to react to a new antigen before class switching

function unkwon

17
Q

Describe IgE

A

invovled in defence agaisnt multicellular paraiste

allergic diseas-e asrthma

18
Q

how do phagocytes bind to opsonised pathognes

A

phagocytes hae antibody Fc receptors-

19
Q

what is VDJ and VJ random combination do?

A

we have multiple versions of variabel diveristy and joining gene segments

hevay chain- CDJ segements

ligh chain- VJ segments

used to geenrate diversity

20
Q

what is the function of RAG?

A

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

21
Q

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

A

Tdt ( terminal deoxynucleotidyl transferase)

joins the VDJ messily

adding extra DNa bases- vriaable region differenet every time

Ds repair protein

22
Q

what sydnrome kis caused by a mutation ins RAG

A

SCID- severe combine dimmunodeificneyc syndrome

23
Q

where does CDJ reocmibation occur?

A

Ig light (VJ) heavy (CDJ)

TCR alpha (DJ) and beta (VDJ)

24
Q

what is B cell tolerance

A

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

25
Q

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?

A

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

26
Q

Describe B cell activation

A

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

27
Q

Describe the Germinal Centre in B cell activation

A

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

28
Q

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

A
  • 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
29
Q

describe isotype class switching

A

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

30
Q

which 4 processes generate antibody diversity

A

combinatorial diveristy (VDJ)

junctional diveristy

affinity maturation

class switching

31
Q

what are C exons

A

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

32
Q

what is junctional diverity

A

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

33
Q

what is affinity maturation/ somatic hypermutation? what is AID

A

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

34
Q

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

A

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 switch site ( locus of class swithcing -rearrnagement occurs)

Activated By AID

xCase 17 SBA (10 decks)

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