Response to antigen Flashcards
If an antigen enters the body intravenously, where is it phagocytosed/pinocytosed?
In the spleen
If an antigen does not enter the body intravenously, where does it go next?
To the lymph node draining that part of the body
How do APCs process exogenous proteins?
- enter APC by pinocytosis
- processed in acidic endosomal vacuoles
How are peptides from exogenous proteins presented?
On MHC class II molecules
How do APCs process viruses and intracellular antigens?
- processed endogenously in APC cytoplasm or ER
- converted to small peptides by proteasomes
How are peptides from viruses and intracellular antigens presented?
MHC class I molecules
When is antibody involved in cell-mediated immunity?
During antibody-dependent cellular cytotoxic reactions (ADCCs) when the effector cell is linked to the target cell via an antibody bridge. Fab portion binds antigen on target cell, Fc portion binds activated effector cell.
Where is CD28 found and what does it bind?
Th cells, binds B7-1/B7-2 (CD80/CD86) on APCs
CD28/B7.1 binding is associated with increased synthesis of:
IL-2 (costimulation)
CD2 is found on:
All T cells
CD2 binds:
leucocyte functional antigen (LFA-3 aka CD48) on APCs and target cells
CTLA4 is found on:
Th cells
CTLA4 binds:
B7-2/B7-1 (CD86/CD80) on APCs
CTLA4/B7.2 binding is associated with decreased synthesis of:
IL-2 (negative regulation)
CD3 is found on
All T cells
CD3 is responsible for:
Activation of T cells
Components of the CD3 complex include:
Three polypeptides (gamma, delta, epsilon) and two zeta chains.
What differentiates Th1 from Th2?
The different cytokines they secrete
What is the primary job of Th1 cells?
Inducing cell-mediated immunity by binding to the peptide-MHC class II complex
What is the primary job of Th2 cells?
Inducing activation of B cells and humoral immunity by binding to the peptide-MHC class II complex and stimulation by IL-2
What do Th1 cells secrete?
IL-2, IFN-gamma, TNF-alpha
What does IL-2 from Th1 cells do?
T-cell and B-cell transformation
What does IFN-gamma from Th1 cells do?
- enhances cell-mediated immunity by activating macrophages and NK cells.
- triggers HLA antigen presentation by endothelial cells
- suppresses antibody formation by down-regulating IL-4 synthesis
What does TNF-alpha from Th1 cells do?
- activates macrophages
- synergizes with IL-1 to stimulate acute phase response
What secretes IL-12 and IL-8?
dendritic cells and macrophages
What do IL-12 and IL-8 do?
- help transition macrophages, Tc cells, and NK cells into cell-mediated immunity mode.
Th2 cells secrete:
IL-4, 5, 10, and 13
What does IL-4 from Th2 cells do?
- development of antibody synthesis by stimulating B-cell differentiation
- necessary for IgE production
- suppresses CMI by IFN-gamma in Th1 cells reducing macrophage activation
What does IL-5 from Th2 cells do?
- synergizes with IL-4 and IL-2 in B cell differentiation
- facilitates IgA synthesis
- growth and differentiation of eosinophils
What does IL-10 from Th2 cells do?
- inhibits Th1 release of IFN-gamma (like IL-4) reducing macrophage activation
What does IL-13 from Th2 cells do?
- mimics IL-4/IL-10 and inhibits Th1 cytokine release
What stimuli are required for B cell differentiation?
- binding of antigen with IgM antigen receptor specific for epitope
- cytokines IL-2 and IL-4
Role of IL-5 in B cell differentiation
stimulation of assembly of H and L antibody chains
Roles of IL-6 in B cell differentiation
terminal differentiation into plasma cell and secretion of IgM
IgM to IgG switching cytokines:
IL-4 and IFN-gamma
IgM to IgA switching cytokines:
TGF-beta
Switch to IgE cytokines:
IL-4
Where is CD40L found?
B and T cells
What does CD40L bind?
CD40
What does CD40 do?
activation
Where is LFA-1 found?
T cells
What does LFA-1 bind?
ICAM-1 on APCs or epithelium
Where is VLA-4 found?
T cells
What does VLA-4 bind?
VCAM-1 on APCs or epithelium
What happens when a CD8 T cell recognizes antigen on an APC but does not receive a second signal?
Anergy
