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SFM Quiz 2 > Antigen Recognition > Flashcards

Antigen Recognition Flashcards

1
Q

receptor types

A

B cell receptors
T cell receptors
antibodies (soluble)

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2
Q

B cell receptors are composed of

A

surface Ig and two invariant chains (Iga and Igb)

these ensure surface expression of immunoglobulin and also function in signal transduction

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3
Q

T cell receptor complex is composed of a

A

aB heterodimer associated with invariant sequence proteins forming the TCR complex

the associated proteins form the CD3 complex to ensure cell surface expression of the TCR and the signal tranduction-CD3Z

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4
Q

overview of lymphocyte development

A
  • committment of progenitor cells
  • proliferation of progenitors
  • sequential and ordered rearrangement of antigen receptor genes
  • differentation of effectors
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5
Q

Clonal selection

A

gene rearrangement events occur in the absence of the antigen.

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6
Q

allelic exclusion is

A

NON specific

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7
Q

clonal selection overview

A

lymphocyte clones with diverse receptors arise in generative lymphoid organs

clones of mature lymphocytes specific for many antigens enter lymphoid tissues

antigen specific clones are activated by antigens

antigen specific immune responses occur

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8
Q

major mechanisms for generation of lymphocyte receptor diversity is

A

combinatorial diversification
junctional diversity
somatic hypermutation

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9
Q

combinatorial diversification

A

multple germ line genes

V-J or V-D-J somatic recombinations

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10
Q

junctional diversity

A

addition of nucleotides during process of D-J or V to DJ joinng

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11
Q

somatic hypermutation

A

point mutations occuring in fully assembled V-J and V-D_J regions during an immune response.

provides a significant source of Ab diversity

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12
Q

mechanisms for accounting for immune diversity for BCR/ab and TCR are

A

identical!

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13
Q

prodcution of heavy chain for BCR is same for

A

production of b chain in the T cells

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14
Q

production of light chain B cells is same for

A

production of A chain in the T cell

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15
Q

somatic hypermutaiton does not occur in

A

TCRs

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16
Q

comibinatorial diversity: VDJ rearrnagment

A
  1. D-J rearranges then

2. V-DJ rearranges

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17
Q

Recombination signal sequences function to

A

provide recognition sites for recognition enzymes that cut and rejoin DNA bits

Ensure gene segments are joined in the correct order, esp. in heavy chain VDJ

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18
Q

RAG1 and RAG2

A

recombination activating genes only made by lymphocytes, encode for these two necessary components of recombinase

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19
Q

Junctional diversity: at the junction between D and J, there is often an insertion of nucleotides which is catalyzed by the enzyme

A

TdT

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20
Q

Junctional diversity: TdT catalyzes the random

A

polymerization of nucleotides into DNa without the need for a template

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21
Q

Junctional diversity: P nulceotides added to asymmetrically cleaved

A

hairpins in a templated manner

this leads to further diversity in teh third hypervariable region

22
Q

Junctional diversity: recombination between V-J and VDJ is not

A

always perfect

errors tht occur in the recombination event that brings the V region next to the J or D regions or the D region next to the J region can lead to frameshifts!

23
Q

Junctional diversity: frameshift errors can

A

triple the diversity generated by DJ and VDJ joinning

the diversity generated by this mechanims occurs in the hypervariable region

24
Q

lots of diagrams..know?

A

know

?

25
Q

the second type of combinatorial diversity happens after both

A

receptor chains have been rearranged, transcribed and translated

26
Q

the two different receptor chains (heavy and light in Ig, or a and B or y and D in TCR) are

A

combined to make the antigen binding site

27
Q

signals from thr pre-BCR are responsible for

A

the largest proliferative expansion of B lineage cells during B cell development

signals to irreversibly inhibit rearrangement of the Ig heavy chain locus on the other chromosome, allelic exclusion

28
Q

allelic exclusion

A

an individual B cell can express one heavy chain encoded by only one of the two inherited alleles

ensures that every B cell will express a single receptor, thus maintaining clonal specificity

29
Q

alternative splicing of heavy chain mRNA: M and D constant regions

A

the pre-mRNA can be processed in two ways, one to bring the VDJ next to the Cu gene and the other to bring the VDK next to the Cd gene

the resulting mRNAs have teh L, V, D, J and Cu or Cd exons continuous and will encode for a mu and a delta chain, respectively

30
Q

distinguishing self from nonself

A

selection deletes or functionally inactivates cells that display antigen receptors that are self-reactive

tolerance is acquired by immature B cells that do NOT become activated when challenged with self-antigen

31
Q

rescue of self-reactive B cells by receptor editing

A

occurs in developmentally arrested, immature B cell

RAG protein synthesis remains on for additional rearrangement of light chain genes

if new light chain is not reactive with self antigen, then tolerance is established and the B cell will mature

receptor editing assesses the compatibility of receptors produced from successive gene rearrangements

DOES NOT OCCUR in T CELLS

32
Q

thymus organization

A

different regions of the thymnus are distinguished by teh cells present and influence the developmental events of T cells

thymic cortex is outer cortical region

medulla is inner cortical region

peaks in puberty and declines after

33
Q

the immature T cells contained within the thymus are called

A

thymocytes

they are embedded in a network of epithelial cells call thymic stroma

express both classes of MHC

34
Q

the thymus is a primary lymphoid organ involved in the

A

production of mature lymphocytes, not antigen presentation

the only route by which progenitor cells enter the thymus and mature T cells leave is via the BLOOD

35
Q

signals for the pre-TCR are responsible for

A

the largest proliferative expansion of T lineage cells during T cell development

signals to irreversible inhibit rearrangement of the B chain locus on the other chromosome, allelic exclusion

36
Q

allelic exclusion

A

an individual T cell can express one B chain encoded by only one of the two inherited alleles

ensures that every T cell will express a single receptor, thus maintaining clonal specificity

37
Q

the TCR will interact with either a

A

class I or class II MHC

combinatino of TCR and co-receptor is double checked

38
Q

double positive thymocures undergo positive selection

A

establishment of self-restirction, recognition of self MHC

39
Q

double positive thymocytes undergo negative selection

A

establishment of central tolerance, T cells do not become activated by self antigen

40
Q

after positive selevtion, thymocytes are self-MHC restricted but

A

they may still be able to react with self-antigen

41
Q

T reg: peripheral supressors

A

small population of self-reactive CD4 T cells become T regs

inhibit self-reactive Th1 cells in teh periphery

express CD4 and CD25 on surface

use FoxP3

42
Q

not all self antigens are present in bone marrow or thymus, some can be

A

tolerized in the periphery if they encounter and respond to self antigen

43
Q

VDJ rearrangement of the heavy chain

A

germline DNA underogoes somatic recombination to make DJ and then another somatic recombination to make VDJ and then Cu and Cd

44
Q

happens by palindromic

A

hairpins that are cut by RAG1 and 2 (VDJ recombinases)

45
Q

juntional diversity occurs at teh

A

hairpin turn between D and J

46
Q

VJ rearrangement on the light chain undergoes

A

the same thing without the D and uses RAG and TdT

47
Q

after DNA rearrangement,

A

transcripton and translation take place as normal

48
Q

memorize two charts

A

charts!

49
Q

Cu and Cd are added via

A

alternative splicing of the heavy regions on B cell receptros

50
Q

B cells that react to self are either

A

killed via apoptosis or made into anergic B cells

51
Q

T cells are initially

A

double positive as CD4 and CD8 and then they are “trained” to bind CD4-MHCII and CD8-MHCI

52
Q

abberant B/T cells can be pruned at three levels

A

at the Pro-B/T cells phase if they fail to express pre-antigen receptor

after the pre-B/T cell phase if they dail to express antigen receptor

and at positive/negative selection. If they have a strong antigen recognition to self, they are negative selevted for and die! weak antigen will be positively selected for and live!

SFM Quiz 2 (25 decks)

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