Lymphocytes and their receptors - Bittencourt Flashcards

1
Q

What are the 3 major types of lymphocytes?

A

T cells

B cells

NK cells

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2
Q

Which cell regulates adaptive immunity and is responsible for cellular immunity?

A

T cells

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3
Q

What are B cells responsible for?

A

Antibody production

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4
Q

When does T cell development begin?

A

Before birth

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5
Q

T cells that express a beta chain become _______

A

ab T cells (most common)

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6
Q

T cells that express gamma or delta chains become _____

A

gamma delta T cells - involved in innate and adaptive, less common

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7
Q

ab T cells

A

most common

involved in adaptive immunity

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8
Q

What part of the immune system do NK cells play a role in?

A

Mostly innate!!

Does participate in ADCC pathway in adaptive immunity

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9
Q

What segments are found on the beta chain of TCR receptors?

A

VDJC segments

  1. Variable region
  2. Joining region
  3. Constant region
  4. Diversity segment
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10
Q

What segments are found on the alpha chain of TCR receptors?

A

VJC segments

  1. Variable region
  2. Joining region
  3. Constant region

** no diversity segment

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11
Q

What segments are found on both alpha and beta chains on TCR’s?

A

variable region and constant region

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12
Q

How does TCR gene rearrangement begin?

A

With rearrangement of beta chain genes in pre-T cells (thymocytes)

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13
Q

How is a ab TCR assembled?

A
  1. Beta chain assembled first
  2. Random joining of Diversity and Joining segments (DJ-beta)
  3. Random linking of DJ-beta segment with Variable segment (DJV-beta segment)
  4. Forms variable region of beta chain

Then alpha is assembled!!

  1. Variable segment and Joining segment make complete alpha chain variable region (VJ- alpha segment)
  2. VJ-alpha segment then joins with C-alpha region = VJC alpha chain
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14
Q

What is RAG1-RAG2 complex?

A

Helps with the recombination of VDJ segments

Cleaves the VDJ segments

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15
Q

What does DNA-dependent protein kinase do?

A

excises the intervening DNA to increase diversity of TCRs

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16
Q

What does terminal deoxynucleotidyl transferase do?

A

Reconnects V and J segments and adds random nucleotides within a coding joint

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17
Q

Where does selection of T cells take place?

A

In the thymus - positive and neg selection

18
Q

What causes thymocytes to undergo apoptosis?

A
  1. no TCR present
  2. Non functional TCR

= apoptosis

19
Q

What is positive selection of T cells?

A

a test to see if new TCRs can bind to MHC molecules

only T cells that bind MHC pass positive selection, if not they undergo apoptosis

96% of Thymocytes fail positive selection

20
Q

Which cells are able to migrate from the thymus?

A

only non-self-reactive T cells can leave

this avoids autoimmunity

21
Q

What is the result of T cells that bind STRONGLY to MHC/self antigen complexes on APCs?

A

Failed negative selection - Apoptosis

22
Q

What is the role of Autoimmune Regulator gene? (AIRE gene)

A

enhances negative selection in the thymus, prevents autoimmunity

helps detect self reactive T cells to kill them ASAP

induces expression of antigens found in other tissues of the body

23
Q

If a thymocyte has high affinity for an MHC II molecule what happens?

A

The thymocyte that is CD4+/CD8+ will turn off the CD8+ gene and begin to solely express CD4+

24
Q

If a thymocyte has high affinity for an MHC I molecule what happens?

A

The thymocyte that is originally CD4+/CD8+ will turn off the CD4+ gene and begin to solely express CD8+

25
What are the CD4+ Th cells?
Th1, Th2, Th17, Treg
26
Where are B cells produced?
In bone marrow
27
Who has more receptors, T cells or B cells?
B cells
28
How many binding sites do B cells have? T cells?
B cells have 2 binding sites T cells have 1 binding site
29
How many polypeptide chains are on a BCR?
4 polypeptide chains - 2 identical heavy chains - 2 identical light chains A constant and variable region in each chain
30
What segments are found on the heavy chain of BCRs?
VDJ segments 1. Variable segment 2. Diversity segment 3. Joining segment
31
What segments are found on the light chain of BCRs?
VJC segments 1. Variable segment 2. Joining segment 3. Constant segment
32
What determines the type of heavy chain on BCR?
constant segment
33
What is first to appear on pro-B cells?
Heavy chains D and J 1. Diversity and Joining
34
How are BCRs assembled?
Heavy chain assembled first 1. D and J segment join 2. V segment joins DJ segment = VDJ segment 3. alpha and beta Poly-Ig chains join Then light chain forms 4. V and J segments join = VJ segment
35
When are light chains rearranged?
at the pre-B cell stage
36
what Igs are found on a mature B cell?
IgM and IgD but IgD has no function
37
What occurs if a immature b cell is stimulated?
leads to cell death or anergy, state of no response
38
When is a B cell at full maturity?
When IgD is expressed with IgM on the surface of the B cell
39
Which chain on a BCR contains a diversity segment?
only the HEAVY chain
40
How are B cells eliminated?
Through negative selection or clonal deletion