HDM - Chapter 3 Flashcards by Justin King

What is the MHC restriction of T-cells?

T cells can only “see” an antigen if presented in an MHC

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What kind of MHC receptors do CD4+ and CD+ T cells recognize ?

CD4 looks for MHC II
CD8 looks for MHC 1

Remeber 4 x 2 = 8 and 8 x 1 = 8

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Where are the classical Dc vs the Pastmacytoid DC found?

Classical DC are found in tissues and 2ndary lymphoid organs

Plastmacytoid blood and tissues

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Characteristics of Classical DC, i.e. 
Surface Receptors
Major Locations
Expression of TLR's
Major Function

Surface DC: CD11c high
CD11b high

Expression of TLR: TLR’s 4, 5, 8 high

Major Cyokines: TNF, Il-6, IL-12

Fnct.: Induce T cell response against MOST antigens

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Characteristics of Plastmacytoid, i.e. 
Surface Receptors
Major Locations
Expression of TLR's
Major Function

Surface DC: CD11c low
CD11b - (not present)

Expression of TLR: TLR’s 7, 9 high

Major Cyokines: Type I INF’s

Fnct.: Antiviral innate immunity and induction of T cell response against antigens

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What occurs when a DC binds an antimicrobial antigen and signaling pathways are initiated?

Loose their ability to stay attached to Endothelial cells and begin to express CCR7 directs them to a HEV to a LN

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Before heading into a LN what else happens to the DC, i.e. what makes a mature DC?

Become able to activate T-cells by up-regulation of:

MHC receptors (INF - Gamma)

costimulators: TLR Ligands
Said know for EXAM 2 only- (CD40/CD40L)

Other T cell activators: B7, ICAM-1, IL-12

Decrease expression of:
Fc/Mannose receptors

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Describe primary property of the DC

Principal inducers of T cell response for NAIVE T cells

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Describe primary property of the MACRO

Ingest Microbes and display to EFFECTOR T cells , upon activation Dec. MHC II

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Describe primary property of the B cell

B-cell display to T helper (EFFECTOR) important for development of Humoral Response -> super activation of T-cells

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How does a B-cell change in response to binding Ag?

Increase MHC II expression with IL-4

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What are the major cells that produce INF-Gamma?

NK’s (primary) and T-cells during adaptive immune reactions

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What does INF-Gamma do?

Increase MHC II expression on APCs

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What increases the activation of MHC 1 ?

INF gamma and Type 1 Interferons

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What is the basic structure of an MHC 1 receptor?

Contains 1 alpha and 1 beta chain, specifically:

Beta 2 microglobulin (invariant)

Alpha chain of three domains

alpha 1 and 2 form the binding cleft for the Peptide
alpha 3 invarient binds to CD8

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What is the basic structure of an MHC II receptor?

Contains 1 alpha and 1 beta chain with two domains

Alpha 1 and Beta 1 compose the binding cleft for pepetide
Alpha 2 and Beta 2 bind CD4

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How many MHC genes do we have?

3 from each parent and they are codominately expressed

What are the three loci for the HLA I, i.e. MHC 1?

HLA-A, HLA-B, and HLA-C

What are the three loci for the HLA II, i.e. MHC II?

HLA-DR, HLA-DQ, HLA-DP

Each of these contributes to an alpha and Beta Chain

What is a MHC Haplotype?

Numerical designation for the Genes, used to denote what specific genes you have

Where is the pocket residues on an MHC receptors found?

Pocket is found on the floor of most MHC receptors serves as an anchor to hold the peptide

Where are the anchoring residues on an MHC receptors found?

The anchor residues are found on the outer edges of the receptor and these can bind most peptides

What is the length of AA’s for MHC 1 vs MHC II recceptors?

MHC I 8 to 10 AA”s

MHC II 10 to 20 AA’s

How are extracellular proteins processed?

Through Endosomes/lysosomes and displayed MHC II

How are intracellular proteins processed?

Through proteosomes and displayed on MHC I

Describe the steps for extracellular proteins processing

1. Internalize through endocytosis or Phagocytosis 2. degrade through lysosome 3 MHC II in ER bound to Ii with CLIP (prevents binding of other ER proteins) is sectreted 4.Sent to the Endosome with the Protein 5. HLA-DM assists 6. Expressed on Cell surface

What are the three things HLA-DM does?

After Ii is degraded; HLA-DM causes: - CLIP to dissassociate from the MHC I - stabilizes the empty MHC II and prevents degredation - Facilitates the bind of the Ag fragments to the binding groove

Describe the steps for intracellular proteins processing

1. Proteins are tagged with Ubquitin for Proteosome 2. Proteins fragments transported to ER trough TRAP stabilized by the chaperone protein Trapasin 3. ERAP (Endoplasmic Reticulum Associated Protein) will modify the peptide so it is the proper length to fit into the MHC 4. Sent to the Cell surface in the Endosome

What is cross presentation?

Cross presentation is the process of taking an External peptides and presenting them on a MHC I receptor

How does cross presentation work?

Some DC's ingest an infected cell, dead tumor cells, microbes etc. and send to a proteosome and then to the ER where they are then presented in a MHC I

What are immunodominant peptides?

the peptide chains of Ag's that can bind to MHC's

What can B-cells receptors bind?

Bind many things like small proteins, polypeptides, polysaccharides, lipids, and small chemicals

What are Follicle Dendritic Cells (FDC)?

Cells found w/in the follicle of a lymph node that concentrate the Ag for presentation to activated B-Cells

Characteristics of FDC's (3)

Not Bone marrow derived Not related to DC's that process and present to T-Cells Ag presented coat with C3b and C3d Compliment proteins or Ab and use FC receptors to bind these complexes

Describe a Killer T Cell

Different and distinct from NK's | Specific against Lipids displayed in Class I like CD1 molecules and gamma/delta TCR's

What is the difference b/w TH1 and TH2 helper cells?

TH1 secrete INF-gamma act on MACRO | TH2 secrete IL-4 pushes B cell proliferation

Describe TCR

Contains an Alpha and Beta Chain's apart of the Ig Super Family Each chain has a constant and variable regions, Ag binds at the variable regions of alpha and Beta

What is the rare variety of a TCR?

Gamma Delta TCR compose 10% and are similar, but contain a broader specificity for unconventional antigens like HSP and phospholipids

What is composed within the TCR complex?

alpha/beta or Gamm/delta dimer associated w/ (2?) CD3

What is CD3 composed of according to DR. S?

1 gamma, 1 Delta, 2 Epsilon and 2 (Z) Zeta chains

How are the expressions of MHC's different on DC, MACRO and B-Cells

DC constitutively expression MACRO low or negative, induced upon INF -Gamma B- Cells consitutively, further inc. with IL-4

What are immuno globin domains?

Domains that are little half loops in the MHC and TCR receptors that contain Di-sulfide bonds