Adaptive immunity, cells & functions - T-cells and Dendritic cells Flashcards Preview

Immunology & Inflammation > Adaptive immunity, cells & functions - T-cells and Dendritic cells > Flashcards

Flashcards in Adaptive immunity, cells & functions - T-cells and Dendritic cells Deck (33)
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1
Q

What is an antigen?

A

Substance capable of stimulating an immune response and activating lymphocytes (proteins, peptides and polysaccharides)

2
Q

What is an epitope?

A

antigenic determinant, part of a foreign protein, or antigen, that is capable of stimulating an immune response (epitopes can be common to different antigens)

3
Q

How do CD4+ T-cells recognize antigen?

A
Through an antigen presenting cell (dendritic cell, B-cell or macrophage) presenting an antigen via its MHC (Major Histocompatibility Complex) class 2
For example used in bacteria infections
4
Q

How do CD8+ T-cells recognize antigen?

A
Through an infected cell presenting an antigen via its MHC (Major Histocompatibility Complex) class 1
For example used in virus infections
5
Q

Where is the primary lymphoid organ and what cell type matures in it?

A

The organ is the thymus, and T-cells mature in it (T-hymus like T-cell)
The vast majority of T-cells die in the thymus while going through the selection processes

6
Q

In the TCR gene segments recombination, what is the CDR3 useful?

A

It is a variable junction where random nucleotides can be added => this helps TCR diversity, allows to recognize a multitude of antigens

7
Q

What enzyme allows VDJ recombination?

A

RAG: Recombination Activating Genes

Non-homologous end joining (NHEJ) machinery

8
Q

What is the selection process of T-cells in the thymus?

A

They first go through a positive selection where they must have a functional TCR, they can either die or continue with the selection process
Than, after becoming either CD4 or CD8, they go through a negative selection where the AIRE (AutoImmune REgulator) enzyme tests for T-cells that are too reactive to self proteins, they can either die or become regulatory T-cells
If AIRE is defected then T-cells will head to secondary lymphoid organs without going through a negative selection => this will lead to autoimmune diseases

9
Q

Where is the MHC class 1 expressed?

A

It is expressed on all nucleated cells

10
Q

Where is the MHC class 2 expressed?

A

It is expressed on antigen presenting cells: dendritic cells, macrophages and B-cells

11
Q

What does MHC polymorphism imply?

A

MHC genes are highly polymorphic: many different alleles are present among the different individuals in the population
We get a combination of MHC from our parents, this increase the presentation possibilities

12
Q

How are antigens presented in MHC class 1?

A

The infected cell degrades the proteins of the antigen (via the proteasome), binds to the MHC1 protein in the endoplasmic reticulum, goes to the membrane via an exocytic vesicle

13
Q

How are antigens presented in MHC class 2?

A

The pathogen gets up-taken by an antigen presenting cell, it gets degraded in a lysosome, meanwhile the MHC2 in the endoplasmic reticulum goes into an exocytic vesicle, fusses with the lysosome where the antigen is, goes to the membrane

14
Q

What co-stimulation does a T-cell need in order to proliferate and differentiate?

A

His CD28 receptors needs to bind to the antigen presenting cell

15
Q

What is the use of memory T-cells?

A

Memory T-cells respond quickly compare to naïve T-cells

Increases the number of antigen specific T-cells

16
Q

What is DISC?
How is it activated?
What happens?
Why is it useful?

A

DISC: Death-Inducing Signaling Complex in T-cells
It is activated when T-cells binds their FAS receptors (CD95)
It activates the induction of cell death
It is useful for T-cell homeostasis and go back to a normal state

17
Q

Where is T-cell activation taking place?

A
  • Naïve T cells constantly recirculate between the blood and peripheral organs (lymph nodes or spleen)
  • Get activated in peripheral lymphoid organs
  • Effector lymphocytes migrate to the sites of infection
18
Q

How do T-cells migrate?

A
Effector T-cells express high levels of adhesion molecules and
chemokine receptors (ligands expressed at the site of infection)
19
Q

What are dendritic cells?
Which immune system are they part of?
What do they activate?

A
  • Dendritic cells represent uniquely well-equipped antigen-presenting cells (APCs): they capture antigens (phagocytosis) and process these antigens into peptides
  • They are part of the innate immune system
  • They activate CD4+ T-cells: the represent the link between the innate and adaptive immune system
20
Q

What are the stimuli of dendritic cells?

A
  • Whole bacteria or bacterial-derived antigens (lipopolysaccharide, LPS, etc.)
  • Inflammatory cytokines
  • Ligation of selected cell surface receptors (Toll-Like Receptors, etc.)
  • Viral products
21
Q

How do dendritic cells mature?

A
  • Dendritic cells maturate by recognizing and responding to pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs)
  • They react through pathogen recognition receptors (PRRs)
22
Q

What is a cross-presentation CDc1?

A
It follows the same MHC class 1 presentation pathway and presents the antigen to CD8 T-cells, but the antigen is exogenous like the MHC class 2 pathway
This is vey important for tumor killing CD8 T-cells
23
Q

What do Th1 cells do?

A

They activate macrophages (starts killing phagocytosed bacteria and secretes cytokines)
They allow IgG switching for B-cells

24
Q

How do Th1 cells differentiate?

A

Via cytokine IL-12 (secreted by activated antigen presenting cells) and IFN-∂ (secreted by T-cells and NK-cells)

25
Q

What do Th2 cells do?

A

Secrete IL-4 (antibody production for mast cell degranulation, intestinal mucus secretion and peristalsis, alternative macrophage activation for tissue repair), IL-13 (same as IL-4 for intestine and macrophage) and IL-5 (eosinophil activation)

26
Q

What do Th17 cells do?

A

Secrete IL-17 (inflammation neutrophil response, anti-microbial peptides) and IL-22 (anti-microbial peptides, increased barrier integrity on the skin)

27
Q

What is Immune tolerance?

A

The capacity of the immune system to NOT react to self-antigens

  • Central tolerance (thymus): deletion of auto-reactive T-cell in the thymus
  • Peripheral tolerance: T-cell anergy (lack of co- stimulation) and regulatory T-cells production
28
Q

What is the FOXP3 gene and why is it important?

A

It is a gene active in regulatory CD4+ T-cells
It has a suppressive function on T-cells, dendritic cells, B-cells, macrophages, etc.
Important to avoid auto-immune diseases

29
Q

Where is the CD40 receptor expressed, what does it bind to, and what does it do?

A
  • CD40L is expressed by activated CD4+ T-cells
  • Binds to CD40 (B-cells, macrophages, dendritic cells and endothelial cells) and
    activate these cells
  • Stimulation of B-cells to produce antibodies and activation of macrophages
    & dendritic cells
30
Q

What is X-linked hyper IgM syndrome?

A

It’s a rare disorder that increases the susceptibility to infections because the CD40 receptor is defected

31
Q

What does the CTLA-4 receptor do and where is it expressed?

A

• It is an inhibitory receptor, important to terminate immune responses
• It is up-regulated on activated T-cells
Expressed by tumor cells to not get killed (therapy for this is checkpoint inhibitor drugs)

32
Q

What does the PD1 receptor do and where is it expressed?

A

• It is an inhibitory receptor, important to terminate immune responses
• It is up-regulated on activated T-cells
Expressed by tumor cells to not get killed (therapy for this is checkpoint inhibitor drugs)

33
Q

What is an autoimmune disease?

A

• Immune reaction against self (autologous antigens)
• Affect 5-10% of the population in developed countries
=> for example: rheumatoid arthritis, psoriasis, etc.