Ch. 10 Immune response to tumor and transplants Flashcards

1
Q

Immune surveillance

A
  • adaptive immune system detects and kills cells that are outgrowth of transformed cells
  • obviously doesn’t always work though
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2
Q

Types of Tumor antigens

A
  • body sees these as foreign
    • normal proteins just over-expressed or expressed in the wrong place
    • mutated proteins
    • products of oncogenes or mutated tumor suppressor genes
    • products of oncogenic viruses
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3
Q

which cell is used to fight tumors?

A

CD8+ CTL’s

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4
Q

how do tumors activate CTL’s?

A
  • all cells have MHC-I so they can present antigens, BUT no co-stims (or most cells don’t have MHC-II) so they can’t activate the CD8+ cells
  • so response to tumor cells requires cross-presentation or cross priming - DC cells eat the tumor cells and present antigens to both CD4 and CD8 T-cells
    • cross- priming - one cell types presents antigens from another cell and activates T- lymphocytes for the tumor cell
  • then the CTL is activated for that and it can go kill tumor cells that present with MHC-I even without co-stimulation
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5
Q

tumor cell evasion strategies

A
  • Antigen loss variants - they stop expressing that antigen that is immunogenic
  • don’t express MHC-I so can’t be killed by T-cells
  • produce natural immune suppressing cytokines - TGF-Beta
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6
Q

Tumor Immuno therapy

A
  • give anti-tumor effectors
    • monoclonal antibodies to stimulate complement or immune
    • Antibodies against CD20 on B-cells in b-cell tumor
    • VEGF in colon cancer
  • stimulae own immune response
    • inject IL-2
  • Adoptive cellular immuno therapy
  • Vaccinations
    • vaccinate with own tumor cells
    • take out DC cells, and expose them to tumor then put them back in body hoping they present tumor antigens
    • plasmids with tumor DNA hope that DC’s pick up
    • inject tumor cells that also express IL-2 or co-stimulators to activate immune system to their antigesn
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7
Q

Types of transplants

A
  • syngeneic - btw two identical animals (or same) - grafts accepted
  • Allogeneic - btw different individuals of same species - rejected
  • xenogeneic - btw individuals of different species - rejected
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8
Q

main rejection in transplants?

A
  • MHC molecules
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9
Q

Direct alloreognition

A
  • Donor MHC on donor APC’s are recognized by host (self) t-cells
  • requires that donation included APC cells
  • ## probably more important in acute rejection and a CTL response
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10
Q

Indirect allorecognition

A
  • Self (host) APC cells ingest the graft and then present alloatnigens (foreign) to host T-cells
  • usually involved in chronic rejection
  • probably invove CD4+ and delayed hypersensitivity
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11
Q

Mixed lymphocyte reaction (MLR)

A
  • Mix host T-cells with donor leukocytes and measure reaction to determine how compatible they are.
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12
Q

Hyperacute graft rejection

A
  • mediated by antibodies
    • they were already present in host - maybe previous transfusions
    • antibodies bind to antigen in donor blood vessel
  • occurs in minutes
  • antibodies activate clotting and complement system
  • leads to thrombosis in graft vessel - main characteristic
  • leads to
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13
Q

Acute graft rejection

A
  • mediated by T-cell attack of graft - mainly CTLs but also T-cells may damage vessels
  • antibodies also involved in vessel damage
  • ## days to weeks
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14
Q

Chronic Graft rejection

A
  • Mediator is again T-cells
  • slow loss of graft function over months to years either from fibrosis or narrowing of graft vessels
  • T-cells react to alloantigens
  • T-cells also secrete cytokines that increase fibrosis and intima growth (smooth muscle)
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15
Q

Cyclosporin

A
  • Blocks Calcineurin - signal transduction pathway for T-cells (important cuz they control graft rejection) that leads to NFAT transcription factor production
  • broad immuno suppressor
  • allows many organ transplantations
  • don’t have to worry much about HLA matching anymore b/c can just suppress immune system with this - when ppl are dying and can’t wait for transplant
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16
Q

problems with immunosuppressors

A
  • increase susceptibility to infeciton
  • increased risk of cancers
  • goal would be to create tolerance just for the graft so you don’t have to turn off the whole immune system
17
Q

considerations for blood transfusions

A
  • must match ABO (type A - has A antigens and therefor antibodies against B)
  • O has no antigens but antibodies in serum against both
    • so O can give cells to anyone b/c no antigen
    • can only accept from O b/c has antibodies against A and B
18
Q

Graft V. Host disease

A

Bone marrow transplants only transplant the hematopoietic stem cells
- if T-cells are transplanted they will attack host tissues