Cell Mediated Immunity Flashcards
What cells are included in cell mediated immunity?
- T-helper cells,
- cytotoxic T cells
- NK cells
What are the subpopulations of dendritic cells?
DC1 and DC2
What is the function of DC1 cells? What do they produce to achieve that?
- produce large amounts of IL-12 (mostly promoted by microbial molecules)
- activate T helper 1 (Th1) cells
What is the function of DC2 cells? What do they produce to achieve that?
- produce IL-1 and IL-6
- activate T helper 2 (Th2) cells
do not produce IL-12!
What are the major lymphocyte populations?
- Helper T cells
- Cytotoxic T cells
- Regulatory T cells
- B cells
What does each T-cell harbor?
~30,000 TCRSs
T-cell receptors
What antigen binding chains do TCRs bind to?
Antigen binding chains – α, β, γ and δ.
What is the antigen presented to TCR by? What cells?
antigen presenting cells:
- dendritic,
- B cells,
- macrophages.
What activates T helper cells?
interaction between TCR and MHC molecules
Explain the co-stimulation of T-helper cells.
CD40
- receptor expressed on antigen presenting cells
- stimulated by CD154 on T cells
CD80
- antigen presenting cells express
- CD80 + CD28 (on surface of T
helpers) activates T helpers,
- CD80 + CD152 inhibits T helpers.
What is the function of CD40?
- receptor expressed on antigen presenting cells
- stimulated by CD154 on T cells
What is the function of CD80?
- antigen presenting cells express
- CD80 + CD28 (on surface of T
helpers) activates T helpers, - CD80 + CD152 inhibits T helpers.
When do Th1 cells differentiate? Via what?
- as a result of
stimulation by DC1 cells
via IL-12
When do Th2 cells differentiate? Via what?
- as a result of stimulation by DC2 cells
- via IL-1 and IL-6
What do Th1 cells produce?
What does this further cause?
IL-2
- activates T cells (especially T regulatory and cytotoxic cells),
- activates B cells,
- activates NK cells,
- activates macrophages.
Interferon-γ (INF-γ)
- inhibits Th2 cells,
- activates Th1 cells,
- activates NK cells,
- activates macrophages.
What do Th2 cells produce? What does this further cause?
IL-4:
- stimulates B cell growth and differentiation,
- activates mast cells
IL-5, IL-13:
- stimulates B cells,
- activates eosinophils,
- activates M2 macrophages.
What is the general function of Th1 cells?
- activate cell-mediated immunity
What is the general function of Th2 cells?
activate antibody-mediated immunity
What are virus-infected cells most often destroyed by?
T cytotoxic cells or Natural killer (NK) cells
Explain the process of the destruction of endogenous antigens.
- viral antigens presented on MHC class I molecules (endogenous antigens),
–> via TCRs - triggering T cytotoxic cell response
Explain apoptosis by the extrinsic pathway.
- each cell has CD95 receptors that harbor death domain
- apoptosis of an infected cell occurs when the cell is triggered by CD95 ligand (CD95L) (possesed by T cytotoxic and NK cells)
- activation of CD95 leads to formation of signaling complex (DISC),
- signaling complex (DISC) activates caspase 8
Explain apoptosis by the intrinsic pathway.
- cytotoxic T cell binds to MHC class I
molecule, - release vesicles with perforins
and granzymes to the infected cell surface - perforins attack cell membrane (form large pores)
- granzymes enter the cytoplasm and
attack mitochondrion (mitochondiron releases cytochrome C to the
cytoplasm) - cytochrome C activates caspase 9
What is the final enzyme released during apoptosis? What does it cause?
caspase 8 (of extrinsic pathway)
caspase 9 (of intrinsic pathway)
–> caspase cascade
What does the caspase cascade do?
- degrades proteins
- activates endonucleases (which degrade DNA/RNA)
- disrupts the structural integrity of cells
