Lesson 3

Question 1

Which is the role of fibroblast? What do they produce?

Answer 1

Fibroblasm produces metalloproteinases, important for the inflammatory response: destroying the extracellular matrix they open the way for the leucocytes to extravasate.
They also release cytokines

Question 2

Hematopoiesis: localization during fetal life and after birth

Answer 2

It happens in the red bone marrow.
During fetal life: liver and a bin in the spleen. After the 5th month in the bone marrow
After birth: bone marrow, firstly in the long bones and then in short bones.

Question 3

Which are the cell types originated by the myeloid precursor? In what do they differentiate?

Answer 3

• Erythroid progenitor => differentiates in red cells
• Megakaryocytes => differentiate in platelets
• Basophil progenitor => differentiates in granulocytes, such as basophils and mast cells
• Eosinophil progenitor => differentiates in eosinophils
• Granulocytes-monocyte progenitor => differentiates in neutrophils and monocytes, when they extravasate, monocytes can differentiate in dendritic cells or macrophages.

Question 4

Which are the differences between our molecules and microbes’ molecules?

Answer 4

• Proteins with mannose residues
• Lypopolysaccaride
• Double strained RNA
• N-formil-metionil-peptids: this is typical of bacterial proteins, however some of our own proteins in the mitochondria are bound to formyl-methionine. Proteins from the mitochondria stay there and they never go out in the cytosol, if this happens it means that the mitochondria are damaged, so the cell may be suffering
• CpG sequences not methylates
  These are all PAMPs

Question 5

Which receptors are present on the surface of immune cell and why?

Answer 5

• PRRs: they’re the most abundant receptors. Some PRRs are exposed on the cell surface, some are free in the cytosol and others are expressed on the endosomal membrane
• Cytokine and chemokine receptors
• Adhesion molecules: they allow the cell to extravasate and adhere to the tissue
• Hormone receptors: the immune system, in some conditions, functions differently in men and women, because it can be modulated by sexual hormones
• Antibody fragments: for complement receptor
• Scavenger Receptors: they recognize lipidic molecules typical of bacteria or damaged cells
• C-type lectin receptors: they recognize sugars on microbes, fungi, lipoproteins secreted by stressed cells
• Toll Like Receptors (TLR): they recognize PAMPs and DAMPs;

Question 6

Toll-like receptors: which mechanism allow them to be able to recognize the ligand? (formation of the complex)

Answer 6

1- MyD88 bind the IL1 receptor associated kinase (IRAK)
2- The phosphorylation of IRAK lead to the binding of TRAF6
3- MyD88-IRAK-TRAF6 bind the TIR domain on TLR
4- TLR dimerize

Question 7

Toll-like receptors: what happens if one of the adaptors (MyD88, IRAK, TRAF6) is absent?

Answer 7

There could be a high sensitivity to infection

Question 8

Toll-like receptors: which can be the pathways activated by the binding of TRF6?

Answer 8

1- MAP Kinase pathway: lead to the activation of AP1, a transcriptional factor
2- Activation of IRF7 (interferon response factor 7): this transcription factor starts the transcription of interferon genes
3- NFkB pathway: it induces the transcription of inflammatory cytokines and chemokines. Its misfunctioning causes severe immunodeficiency

Question 9

Toll-like receptor: descrive the NFkB pathway. What’s the result?

Answer 9

1- A barrier has been broken and the bacteria enter the cell
2- The TLRs recognition induce the production of cytokines (TNF and interferon)
3- A positive feedback mechanism activates macrophages
4- NK and T cells are recruited and activated
5- IL12 and IFN-γ are produced and act on dendritic cells
6- Dendritic cells start to phagocytise, change their shape and increasing the expression of MHC (became mature dendritic cell). They move to the lymphoid organ and activate the active immunity by secreting factors that increases the expression of chemokine’s secretion

Question 10

Which could be the consequences of non-functioning toll-like receptors?

Answer 10

It they aren’t activated there could be an immunodeficiency.
If they’re too much active there could be an autoimmune disease

Question 11

Which are the types of cytosolic receptors? (list)

Answer 11

• NLR (nod like receptors): recognize some peptidoglycans
• RLR (rig like receptors): recognize viral DNA
• CDS (cytosolic DNA sensor): recognize bacterial DNA

Question 12

Which is the role of NOD like receptors?

Answer 12

1- bind a nucleotide thanks to their nucleotide-binding domain
2- inflammmasome is formed and it activates the caspase 1
3- caspase 1 cleaves the pro-IL1 allowing the release of the active form

Question 13

NOD2: which pathway is activated by NOD2?

Answer 13

NDkB pathway leading to an inflammatory response

Question 14

What does RIG like receptors recognize?

Answer 14

helicase domain: viral dsDNA

Question 15

RIG like receptors: which kinds are there?

Answer 15

RIG and MDA5

Question 16

What are cytosolic DNA sensors?

Answer 16

Proteins that can recognize viral DNA in the cytoplasm and develop an antiviral response (es: interferon type 1 and autophagy)

Question 17

Which are the families of CDS?

Answer 17

• STING: stimulator of INF genes, active the transcription of INF1 and the autophagy mechanism
• DAI: DNA-dependent activator of INF-regulatory factors, binds viral DNA and activates IRF3 leading to INF1 production

Question 18

Which are the types of interferon?

Answer 18

• Type 1: INFα, INFβ
• Type 2: INFγ
• Type 3: INFλ, INFω

Question 19

General features of the interferon?

Answer 19

• they bind heterodimers receptors (α and β)
• they don’t have a kinase activity themselves (need to bound by a JAK or a TYK)

Question 20

What’s the activity of the interferon? What does it do when activated?

Answer 20

The transphosphorylation of the cytosolic tails allows the dimerization of STAT2/STAT1 (INF I and INF III) and STAT1/STAT1 (INF II), these complexes translocate into the nucleus and modulate the activation of genes for the fighting of viral infections.