Innate Immunity: Phagocytosis and Atg Presentation

Question 1

How many fates has a pathogen when it binds to Dendritic cells?

Answer 1

2

Question 2

Fate 1 of pathogen:

Answer 2

Binds to TLR on Dendritic cell
Co-stimulatory molecules present to Naive T cells or inflamm cytokines present to naive T cells
Naive: Th1–> interferon gamma or Th2—> IL-4

Question 3

Fate 2 of pathogen:

Answer 3

Phagocytosis (now encapsulated)
Antigen presentation to…
Naive T-cells, from here the response is the same

Question 4

Antigen binding

Answer 4

1. Its epitop can bind to IgG, the costim factor in this case would be C3b (complement system?)
2. PAMP

Question 5

2 fates after the phagocytosis

Answer 5

Inflamm- Ne granulocytes

Presentation- MHC complex on the dendritic cell has to be recognised by a CD8 T-Cell, this is the MHC restriction

Question 6

Antigen presentation: location and the cells involved

Answer 6

1. In the peripheral tissues: APC’s, when they bind the antigens they become activated (APC is usually a dendritic cell)
2. In the lymphoid organs: Antigens are presented to a Naive T-cell- this causes T-cell activation
   Replication of the antigen specific T-Cells
3. In the peripheral tissues: T-Cells become specialized
   Effector cells activate other immune cells and kill target cells
   Memory cells- for another infection

Question 7

Major Histocompatibility Complex: 3 classes (genes)

Answer 7

MHC I
MHC II
MHC III

Question 8

MHC I (5)

Answer 8

Peptides
Nucleated cells*
Endogenous Atg receptor 
CD8 T-Cell
Cytotoxic Tc

Always has to present aa’s for NK and Tc
Missing in tumors!

Question 9

MHC II

Answer 9

Peptides
APC's (monocytes and dendritic cells)
Exogenous Atg receptor 
CD4+ T-Cell
Th

Activate the T-helper!

Question 10

MHC III

Answer 10

Peptides linked with immune response
Complement
TNF
Heat shock proteins

Question 11

MHC I Presentation

Answer 11

Location: on all nucleated cells
High conc on B, T, macrophages
Exceptions: early embryonic life

Function:
Endogenous Atg presentation
Cellular immunity (Tc and NK)
Always presents either self or foreign

Presentation:
The endogenous protein Atg goes to the Proteosome and becomes a peptide fragment of 8-9 aa’s and now enters the endoplasmic reticulum

Question 12

MHC II Presentation

Answer 12

Location: On APC’s
permanently on B-cells, macrophages, dendritic cells
transiently induced on activated T-Cells, blood vessels

Function:
Exogenous Atg presentation
Th activation

The Atg binding site is 10-20 aa’s, is located btw the alpha and beta chain

*look at diagram for the entire presentation

Question 13

Atg presentation on CD1

Answer 13

Presentation of foreign and self-lipid components e.g LPS

Structurally similar to MHC - heterodimer with beta2 microglobulin, it’s binding site is larger than in MHC I

Location:
APC’s- most active on DC’s
B-cells
Intestinal epithelium