1-T Lymphocytes Flashcards

1
Q

general characteristics

A

-subset of lymphocyte family with B cells and NK cells
-cannot be distinguished from B cells morphologically
-only recognize antigen with APC and MHC unlike B cells

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2
Q

ontogeny

aka where they come from

A
  1. prothymocytes from bone marrow
  2. thymus for maturation
  3. peripheral lymphoid organs
  4. blood stream until directed for cell mediated immune response
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3
Q

T helper lymphocytes aka CD4 subsets

A
  1. TH1 = cell mediated immunity (macrophages, IgG syn)
  2. TH2 = humoral immunity (mast cells, eosinophils, IgE syn)
  3. TH17 = enhances inflammation
  4. TFH = promote proliferating B cells/germinal centers in lymphoid organs
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4
Q

cytotoxic T lymphocytes

A

aka CTLs/CD8
lyse virus infected cells

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5
Q

regulatory T lymphocytes

A

aka CD4 or Treg cells

downregulate immunity

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6
Q

T cell antigen receptor

A

sites for antigen peptide residue + MHC residue
-30,000 identical copies of TCR in T cell surface

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7
Q

TCR structure

A

heterodimer of disulfide linked alpha/beta chains
-each chain has constant and variable region but only 1 antigen binding site

cytoplasmic tails not long enough to act as signal transducer across plasma membrane

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8
Q

CD3

A

required for signal transduction of T cells so expressed on every T cell but dont have anything to do antigens

made of invariant polypeptides (1 gamma + 1 delta + 2 epsilon + 2 zeta)

phosphorylation site on cytoplasmic tail for signals

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9
Q

co stimulatory molecules

TCR

A
  1. CD28 on T cell binds B7 on APC
  2. CD40L on T cell binds CD40 on APC
    B7 and CD40 expressed on all professional APCs

end goal to enhance T cell proliferation ‘build army before attacking antigen’

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10
Q

CD4 accessory protein

A

transmembrane glycoprotein of single polypeptide on majority of mature T cells
-small quantities on surface of macrophages

most CD4 expressing lymphocytes are T helper cells

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11
Q

CD4 function

A
  1. cell adhesion
  2. signal transduction
  3. restricts T cell response to class II MHC
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12
Q

CD8 accessory protein

A

homodimer or heterodimer with alpha/beta chains

most CD8 expressing lymphocytes are cytotoxic T lymphocytes (CTLs)

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13
Q

CD8 functions

A
  1. cell adhesion
  2. signal transduction
  3. restrict T cell resp to class I MHC
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14
Q

signal transduction pathway

A
  1. binding of TCR to MHC to initate activate T cells
  2. early activation- PKC and other kinases activated to phos transcription factors
  3. gene transcription- AP 1 initiates IL-2 cytokine production
  4. mitosis- expand antigen specific clones to amplify immune response
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15
Q

TH1 development

A
  1. IL-12 from inflamm develop naive T cells
  2. interferon gamma IFN-y directs toward cell mediated immunity with active macrophages and CTLs

-CTL differentation via CD4 helper T cells producing cytokines and enhancing APC ability to stimulate differentiation

IFN-y most potent activator of macrophages

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16
Q

TH2 cell development

A
  1. naive exposed to IL-4
  2. direct immune resp toward IgE production for anti-parasite defense
  3. produce IL4, IL5, IL13

if no inflammation then immune resp default to TH2

17
Q

TH17 cell development

A
  1. naive exposed to IL-1, IL-6, TGF-beta from dendritic cells during anti microbial and inflamm
  2. produce IL-17 and IL-22 to promote inflam
18
Q

regulation of TH1 and TH2

A

IFN-y from TH1 will inhibit TH2
IL4 and IL13 from TH2 inhibit TH1

antagonistic effect

19
Q

CTL activation

A

function to destroy intracellular microbes (virus, bacteria) or tumor cells or transplants
-part of cell mediated immunity by TH1

recognize endogenous peptides on class I MHC thru antigen recog with TCR and CD8

20
Q

CTL killing process

primary mechanism

A
  1. target cell binding by recog class I MHC and antigen
  2. CTL activation
  3. lethal hit thru granule exocytosis, perforin makes pores for granzyme B to enter target and activate caspase pathway
  4. disengagement from target cell
  5. death via apoptosis
21
Q

CTL killing mechanism

secondary

A
  1. bind CTL expressed Fas ligand to target cell Fas protein
  2. activate caspases
  3. apoptosis