Immune Cell Interactions Flashcards
Describe the BCR and Ig alpha/beta complex.
- structure: membrane immunoglobulin, associates with Ig alpha/beta complex
- function: receptor-mediated internalization of antigen
Describe the TCR and CD3 complex.
- Structure
- TCR: alpha and beta subunits
- associates with CD3 complex
- Function
- interacts with MHC to recongize antigens
- CD3 acts as signal transducing subunit
What are the surface molecules that interact with MHC?
CD4, CD8
Define CAMs.
- Cellular Adhesion Molecules
- facilitate T cell adhesion
- augment signaling thru TCR
What are the Ig Superfamily of CAMs?
- structure based on Ig fold
- ICAM-1, ICAM-2, CD2, CD4, CD8
What are the Integrin Family of CAMs?
- heterodimers of alpha and beta chains
- LFA-1, MAC01, p150, p95
What are the Selectin Family of CAMs?
- extracellular portion is lectin domain
- binds to carbohydrate ligands, facilitate interactions between leukocytes and endithelium
- L-selectin, P-selectin, E-selectin
What are the Vascular Addressins CAMs?
- molecules w/ carbohydrate ligands recongized by L-Selectin
- CD34, GlyCAM-1
How does signaling between T Cells and APCs work?
- multiple interactions of CAM pairs
-
LFA-1 (integrin) on T cell interacts with ICAM-1 on APC
- signal is weak unless TCR also connects with MHC II + peptide on APC -or- chemokine binds to T cell
- integrin switched to high affinity state, T cell and APC interaction produces strong signaling
-
CD2 on T cell interacts with LFA-3 on APC
- promotes cell adhesion
- augments signal thru TCR
How does signalling between naive T cells and HEVs work?
- L-selectin on naive T cell interacts with sulfated sialyl-Lewisx motif on GlgCAM-1 and **CD34 **molecules of the HEV cell surface
- initiates rolling of naive T cell along endothelium so it can enter blood
What are the T Cell co-stimulatory molecules?
CD28 (positive) CTLA-4 (negative)
Describe the naive T Cell co-stimulatory mechanism.
- naive T cells require TCR/CD3 activation and a second, co-stimulatory CD28 signal to be activated
- **CD28 **on T cell interacts with B7 on professional APC
Describe the negative co-stimulatory mechanism.
- CTLA-4 on naive T cell binds to B7 on APCs
- outcompetes CD28, modulates T cell immune response
SUMMARY REVIEW: What are the T cell surface molecules responsible for antigen recognition?
TCR
SUMMARY REVIEW: What are the T cell surface molecules responsible for signal transduction?
CD3, CD4/CD8, CD2
Co-stimulation: CTLA-4, CD28
SUMMARY REVIEW: What are the T cell surface molecules responsible for adhesion?
LFA-1, L-selectin, CD2
Describe the B Cell co-stimulatory mechanism.
- B cell and T cell interact for antigen presentation
- B cell: MHC, B7
- T cell: TCR, CD28
- CD40L on T cell is expressed
- **CD40 **on B cell interacts with CD40L
- B cell proliferation
Describe the immunological synapse and SMACs.
- point of interaction between T cell and APC
-
c-SMAC: center of cluster
- T cell: TCR/CD3
- APC: MHC/Ag
-
p-SMAC: border of cluster
- T cell: LFA-1
- APC: ICAM-1
- formation initiates T cell signaling

Name and define the methods of action for cytokines. Examples?
- autocrine: cytokine acts on secreting cell
- ex. Il-2 during T cell activation
- paracrine: cytokine acts on neighboring cells
- ex. chemokine recruitment of leukocytes to site of inflammation
- endocrine: cytokine acts systemically
- ex. IL-1, IL-6, TNF-alpha in septic shock
What is the function of IL-2?
helps to activate naive T cells
Describe the IL-2 receptor and its regulation.
- part of common gamma chain family of receptors
- on naive T cells, expressed as form w/ only beta & gamma chains
- when secreted IL-2 binds, alpha chain of IL-2R binds with beta & gamma increases affinity of IL-2R
- IL-2: IL-2R binding signals T cell proliferation
What is the process for neutrophil extravasation to a site of infection?
- rolling: selectin on endothelium binds to carbohydrate ligand on neutrophil
- activation: chemokine binds to GCPR on neutrophil to activate **integrin **
- firm adhesion, transmigration: **integrin **on neutrolphil binds to ICAM on endothelium
What is LAD? What’s the molecular basis?
- Leukocyte adhesion deficiency
- caused by beta-integrin gene mutation, neutrophils can’t get out of blood stream
- suffer from bacterial and fungal infections
What is the function of MHC (HLA)?
when bound to peptide, they interact with TCRs


