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Immunology > B and T Lymphocyte Receptor Diversity > Flashcards

B and T Lymphocyte Receptor Diversity Flashcards

1
Q

compare and contrast BCRs and antibodies

A

BCRs and antibodies have the exact same structure, but antibodies are secreted and released by B cells while BCRs are membrane-bound

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2
Q

how many polypeptide chains make up a BCR? what 2 categories do they fall into?

A 
4;
2 light (L) chains and 2 heavy (H) chains
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3
Q

what does the antigen-binding region of a BCR consist of and what is it referred to as?

A

consists of both light and heavy chains and is referred to as Fab (fragment antigen-binding)

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4
Q

how many Fab regions are on each BCR?

A

2 Fab regions on each BCR

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5
Q

what does the non-antigen-binding region of a BCR consist of? what is it referred to as?

A

consists of heavy chain only, referred to as Fc (fragment crystallizable)

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6
Q

how many antigens can each BCR bind at once?

A

2

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7
Q

what must be done to ensure that BCRs can bind lots of different antigens?

A

generate diversity at Fab region

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8
Q

what are the 2 regions of the Light chains of BCRs?

A

variable (VL) region and constant (CL) regions

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9
Q

describe the variable regions of Light chains of BCRs

A

hyper-variable from one cell to another

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10
Q

describe the constant regions of Light chains of BCRs

A

have either lambda or kappa genes

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11
Q

what two regions does the heavy chain AT THE Fab REGION of a BCR have?

A

has a variable (VH) and a constant (CH) region

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12
Q

describe the variable region of the heavy chain at the Fab region of a BCR

A

hyper-variable from one cell to the next

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13
Q

describe the constant region of the heavy chain at the Fab region of a BCR

A

is consistent from one cell to the next within a response, will be one of 5 options

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14
Q

what do the 5 heavy chain constant region classes correspond to?

A

the type of antibody produced

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15
Q

what are the 5 heavy chain classes and what type of antibody do they produce?

A
  1. mu: IgM
  2. delta: IgD
  3. gamma: IgG
  4. alpha: IgA
  5. epsilon: IgE
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16
Q

how is immunoglobulin/BCR diversity generated in the variable regions or light and heavy chains? (2)

A
  1. gene recombination

2. gene conversion

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17
Q

describe gene recombination to generate diversity in the variable regions of BCRs (4)

A
  1. 2 genes of L chain on the variable region are randomly selected
  2. 3 genes of H chain on the variable region are randomly selected
  3. combination of unique Vl and VH, which rearrange independently of each other create a unique combination that
  4. joins with the constant region during recombination to make super random and diverse BCRs
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18
Q

describe the gene recombination of the L chain of the BCR variable region

A

there are many versions of V genes and J genes and once of each is randomly selected

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19
Q

describe the gene recombination of the H chain of the BCR variable region

A

there are many versions of V genes, D genes, and J genes and one of each is randomly selected

20
Q

describe the gene recombination of the constant region of the light chain of BCRs

A

random selection of either lambda or kappa genes

21
Q

when does gene conversion occur in BCRs

A

when there are limited V gene options

22
Q

what are pseudogenes?

A

sequences of DNA that are upstream of the V gene that do not code for anything but can be used to generate diversity

23
Q

describe the process of gene conversion, which is mostly just for V genes (4)

A
  1. uracil will randomly be inserted in V gene
  2. uracil is then removed bc it is RNA, leaving a gap in the DNA
  3. randomly selected short segments from pseudogenes will be inserted to fill the gap
  4. now are left with different DNA sequence to make a different V gene
24
Q

what will TCRs only bind to?

A

antigen expressed on MHC

25
Q

what do T helper cells recognize?

A

antigen expressed on MHC II

26
Q

what do cytotoxic T cells recognize?

A

antigen expressed on MHC I

27
Q

what are the 2 classes of TCR?

A
  1. alpha:beta (the majority)

2. gamma:delta

28
Q

describe the structure of TCRs

A
  1. 2 polypeptide chains

2. each chain has 1 variable and 1 constant region

29
Q

which region of a TCR recognizes antigen/MHC complexes?

A

the variable region

30
Q

how is diversity of TCRs achieved?

A

through gene recombination

31
Q

describe gene recombination in alpha:beta TCRs

A
  1. alpha chain: has a V, J, and C (Constant) gene; the random selection of 1 V and 1 J gene are combined with the one constant gene of the alpha chain for diversity
  2. beta chain: random selection of 1 V, 1 D, and 1 J gene are combined with one of 2 possible C genes
32
Q

give one big exception/cool thing about generation of TCR diversity in the beta chain that leads to more diversity

A

D gene selection is optional and you can also select for more than one D gene, increasing the number of possibilities

33
Q

where does junctional diversity occur?

A

where the different selected genes join

34
Q

what are the 2 types of junctional diversity?

A
  1. base insertion

2. base deletion

35
Q

describe base insertion of junctional diversity

A

random nucleotides inserted at V, D, and J junctions

36
Q

how many nucleotides can randomly be added between V and D genes in base insertion?

A

up to 5

37
Q

how many nucleotides can randomly be added between D and J genes in base insertion?

A

up to 4

38
Q

describe base deletion of functional diversity

A

random nucleotides may be removed

39
Q

where is MHC I found?

A

on all nucleated cells

40
Q

what is MHC I recognized by?

A

cytotoxic T cells

41
Q

where is MHC II found? (3)

A
  1. dendritic cells
  2. macrophages
  3. B cells
42
Q

what is MHC II recognized by?

A

helper T cells

43
Q

what does MHC I do?

A

presents antigen from intracellular/endogenous locations

44
Q

what is presented on MHC if normal cellular processes are occurring? what is the result?

A

self-antigen is presented and there is no immune response

45
Q

what is presented on MHC I if a cell is infected with a virus or something? what is the result?

A

non-self antigen is present and initiates an immune response

46
Q

what does MHC II do?

A

presents antigen from exogenous locations

47
Q

describe MHC II’s present of mostly non-self antigen

A

antigen is phagocytosed/endocytosed, processed, then presented on MHC II

Immunology (13 decks)

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