IMMUNOLOGY - Cell Mediated and Humoral Immunity (Adaptive) Flashcards
The activity of NK cells is enhanced by which immunomodulators? (3)
IFN-gamma, IFN-beta, IL-12
NK cells kill viral or bacterial cells?
viral
what is the antibody-independent NK response to viruses? (3 steps)
(1) Normal cells express MHC-1 and activation ligand receptors, which NK cells have receptors for - MHC-1 receptor inhibits NK cell activation
(2) In Virus infected cells, MHC-1 receptors are downregulated, and so NK receptors are activated
(3) NK cells release perforin and granzymes which lyse target cells and induce apoptosis
What is the pathway of antibody-mediated NK cell response? (3)
1) NK cells express receptors for the Fc region of IgG (CD16 and CD56 receptors)
2) When antigen is attached to IgG, the Fc portion goes towards CD16 receptor of NK cell and NK cell becomes activated
3) NK cell induces destruction of antibody - antibody dependent cell mediated cytotoxicity
What are the receptors on the B cell membrane? How are they formed?
B cell receptors for IgD antibodies. –>
They are formed by recombindation to form different types of B cell receptors with different binding domains.
What is the process of B cell activation?
Antigens enter lymph node and bind to B-cell receptor.
Cause clarithin coded membrane-mediated endocytosis, activates chromosome 6 to increase MH2 receptor proteins which binds to foreign antigen and to translocate to cell surface to become an antigen presenting cell.
Which cells are antigen-presenting cells.
B-cells, macrophages and dendritic cells
What is the difference between MHC1 and MHC2 receptors?
All nucleated cells have MHC1 receptors with SELF antigens
All APC cells have MHC2 receptors with FOREIGN antigens.
What is the mechanism of t-helper cell activation from MACROPHAGE. (primary signal and co-stimulation/secondary signal)?
Which cytokines are released from T-helper cell?
naive T helper cell has t-cell receptors (TCR) which binds to foreign antigen from APC.
CD4+ receptor on T helper cell surface bind to MH2 receptor on APC cell surface.
This above complex activates CD3 on intracellular side to send signals to nucleus to produce primary signal.
CD28 receptor interacts with B7 protein on the macrophage to activate co-stimulation.
IL-1 secreted by macrophage acts on T-cell receptor to produce intracellular third signal to nucleus.
Cytokines produced include
1. IL-2 (autocrine)
2. IL-4
3. IL-5
IL-2 and IL-4 are the main reasons why T-helper cell divides into TH2 cell.
What can T helper cell differentiate into?
TH1 cell (needs stimulation from IL-12/IFN-gamma)
TH2 cell (needs stimulation from IL-4/IL-10)
How is a B lymphocyte activated?
IL-4 induces CLONAL EXPANSION:
activates the B-lymphocyte to cause B-lymphocyte into more activated B-lymphocytes with MHC2 molecules with foreign antigen and B-cell receptors related to foreign antigen
IL-5 induces DIFFERENTIATION
expanded clonal B cell lymphocytes and becomes plasma cells or memory B-cells.
plasma cells then start secreting antibodies specific to foreign antigen
How is a cytotoxic T-cell activated?
recognises cancerous or viral cell as viral peptides enter the MHC-1 complex.
CD8+ receptor and MH1 complex bind together, as well as T-cell receptor with viral peptide in MHC-1 receptor to avtivate perforins and granzymes
What are the effect of perforins?
What are the mechanism effect of granzymes?
perforins create pores in cancerous cells
granzymes move through pores to activate pro-apoptotic genes (BAX) which binds onto BCL-2 on mitochondrial membrane, and removes BCL-2 from the membrane to initiate cytochrome C –> initiates caspases and cause proteolytic destruction inside the cell –> cell death.
What’s the difference between humoral and cell mediated immunity?
Humoral - humoral fluid –> exogenous antigens freely flowing. B-cell response for antibody response
Cell mediated –> responds to endogenous proteins (viral/cancerous). Cytotoxic cell cell mediated
Which cells do NK cells respond to? (3)
- No MHC-1 receptor cells (all cells are nucleated
- MICA cells (related to MHC-1 but do not have B subunit in their structure)
- IgG antibodies.
What are the 3 signals required for T cell activation?
- TCR of T-cell + MH II of APC (having peptide)
- Co-stimulation by co-stimulatory molecules (CD28 of T cell interacts with B7 protein of APC (CD80/CD 86) –> prevents T-cell from entering anergy state
- interleukins
What is the difference between CD4 T-cell activation and CD8 T-cell activation?
See diagram.
What is the differentiation pathway from Th0?
See answer.
