Term
Three types of antigen presenting cells
of these, which one is not phagocytic? |
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Definition
- macrophages (mononuclear phagocytes)
- Dendritic cells
- B lymphocytes
- B lymphocytes are not phagocytic |
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Term
| Journey of langerhans cells |
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Definition
- form a continuous cellular sheet at the junction of the dermis and epidermis
- migrate via afferent lymphatics into the paracrotz ofthe draining lymph node
- in paracortex, they interdigitate with T-lymphocytes, presenting antigen carried from the skin to immune responisve cells |
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Term
Two lineages of dendritic cells
what important thing is produced by one of these? |
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Definition
1) conventional
2) plasmacytoid - produce large quanitties of interferon in response to viral infections
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Term
| When is B lymphocyte antigen presentation most important? |
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Definition
| - secondary antibody responses |
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Term
| Four steps in MHC class I presentation |
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Definition
1) Virus infects cell
2) Viral proteins synthesized in cytosol
3) Peptide fragments of viral proteins bound by MHC class I in ER
4) Bound peptides transported by MHC class I to the cell surface |
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Term
Where do peptide fragments bind MHC I?
How do they get there? |
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Definition
- Endoplasmic reticulum
- TAP-1 and TAP-2 transporters |
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Term
What are molecules help MHC assemble in the ER?
Where does the MHC go once bound in ER to peptide?
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Definition
- chaperones: calnexin, Erp 57, calreticulin
- through golgi appartatus to celll surface |
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Term
| If a cell is not infected with a virus, what peptides does it go to the surface bound to? |
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Definition
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Term
| Peptide loading of MHC I in ER |
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Definition
1) Partly folded MHC class I alpha chain binds calnexin
2) B2-microglobin binds and calnexin releases the a:B2
3) MHC binds a complex of chaperone proteins (Erp57 and calreticulin)
4) MHC binds TAP with help of Tapasin
5) TAP delivers degraded peptide fragments to ER
6) peptide fragment binds MHC I molcule and it completes its folding
7) MHC is released from TAP complex and exported to PM |
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Term
| MHC class II antigen processing steps |
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Definition
1) After formation in ER, MHC II molecules are loaded with invariant chain, which blocks binding of peptides and misfolded proteins
2) Invariant chain is cleaved in the acidfied endosome, but leaves CLIP in binding a1/b1 binding cleft
3) CLIP blocks binding of degraded fragments when endosome fuses with phagocytized vesicle
4) HLA-DM binds to the MHC molecule, releasing CLIP and alloiwng other peptides to bind
5) MHC molecule then goes to the surface |
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Term
| Two signals required to activate a naive T cell by antigen |
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Definition
1) presentation of antigen by MHC and recognition by T-cell receptor
2) Interaction between CD28 on the Tcell and B7 on the APC |
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Term
| What happens if APC does not have B7? |
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Definition
- The T-cell CD40L (CD154) which will engage CD40 on the surface of the APC
- Interaction of CD40L on the T Cell and CD40 on the APC induces the APC to express B7 |
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Term
| Requirements for B-cell production of antibodies |
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Definition
| After a B cell has presented and activated a T cell, the interaction of CD40 and CD40 L on the T cell indcues the T cell to produce cytokines, which make the B cell proliferate and differentiate into plamsa cells that secrete antibody |
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Term
| What happens inside the T-cell within seconds of MHC-peptide engagement? |
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Definition
| - TCR initiates a phosphorylation cascade sufficient to trigger effector function (such as execution of targe cells) |
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Term
| What is the purpose of the immune synapse? |
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Definition
- mechanism of sustained TCR engagement
- specialized contact with a cluster of TCR's in the middle surrounded by a ring of adhesion molecules |
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Term
| What molecules are important in the immunological synapse? |
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Definition
- LFA-1 (on T cell)
- I-Cam-1 (on APC surface) |
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