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Immunology > Adaptive Immunity > Flashcards

Adaptive Immunity Flashcards

1
Q

What are the main 3 types of lymphocyte which come from the same precursor cell?

A

Natural killer cells
T cells
B cells

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2
Q

What is an antigen?

A

An antigen is a unique part of a pathogen

-antigens are what lymphocytes recognize to mount an immune response

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3
Q

What are the primary lymphoid organs and what is their role?

A

Bone marrow, and thymus

-the sites of lymphocyte development and maturation from bone marrow-derived stem cells

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4
Q

What are the secondary lymphoid organs and what is their role?

A

Lymph nodes, spleen, mucosa-associated lymphoid tissues (MALT)
-the site where immune responses are coordinated

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5
Q

Where are B-cells produced and matured?

A

Produced and matured in the bone marrow

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6
Q

What are the function of B cells?

A

Express a receptor which binds to a specific antigen

-binding to an antigen produces proliferation, maturation and production of soluble receptors called Antibodies

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7
Q

Where are T-cells produced and matured?

A

Produced in bone marrow but mature in the thymus

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8
Q

What are the 3 different types of T cells?

A

Cytotoxic T cell
Helper T cell
Regulatory T cell

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9
Q

What is the function of a T cell?

A 
Express a receptor that binds to a specific antigen
-Can have one of 3 outcomes
Cytotoxicity
Help of other immune cells 
Regulation (turning off immunity)
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10
Q

How does a lymphocyte respond differently to different antigens?

A

Each individual lymphoctye has a different T cell or B cell receptor which binds to a different antigen. Means each cell will respond to a certain pathogen and the immune response can be tailored for that pathogen

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11
Q

How are different T and B cell receptors made?

A

TCR gene= T cell receptor gene
BCR gene= B cell receptor gene
The TCR and BCR genes are chopped up into segments and stuck back together in different orders to make different receptors

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12
Q

What is the difference between antigens B and T cells bind to?

A

B cells bind directly to an antigen even if it’s still attached to a pathogen
T cells bind to antigens that have been chopped up and presented to them by antigen-presenting cells

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13
Q

What 3 signals do T cells need to be activated?

A
  1. T cell receptors binding to a specific antigen presented by major histocompatibility complex (MHC) molecules
  2. Costimulation (B7 family molecules)
  3. Cytokines (interleukins 4,10,12,23)
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14
Q

What does MHC stand for?

A

Major histocompatibility complex

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15
Q

What are the 2 types of antigen presentation?

A

MCH I

MCH II

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16
Q

Describe MCH 1 antigen presentation

A
  • Infection of body cell by virus
  • Virus is chopped up by the proteosome
  • Antigens loaded onto the MCH I in the endoplasmic reticulum
  • Activates CD8+ cytotoxic T cells
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17
Q

What is the function of cytotoxic T cells?

A

Kill the cells expressing MCH I and foreign antigen by:

  • Perforin
  • Interaction of Fas with Fas-ligand on the infected cell
18
Q

Describe the process of cytotoxic T cell killing with perforin

A
  • T cell binds to antigen presented by MHC I
  • Adhesion molecules such as LFA-1 bind the T cell to the target cell
  • Perforin released forming a cyclindrical pore in the infected cell
  • Granzymes released and enter target cell
  • T cell detaches
  • Target cell dies from apoptosis
19
Q

Describe the process of cytotoxic T cell killing using the Fas-Fas ligand

A
  • Fas ligand is on T cells
  • Fas is on target cell
  • Fas ligand-Fas interaction activates FADD which activates caspase 8
  • Activated caspase 8 activates caspase 3
  • Caspase 3 causes the target cell to die via apoptosis
20
Q

What is the difference between normal antigen-presenting cells (APC’s) and professional ones?

A
  • All cells can present antigen to CD8+ cytotoxic T cells on MHC I molecules
  • Only professional antigen presenting cells can present antigen to CD4+ helper T cells on MCH II molecules

-Professional cells express MCH II, costimulatory molecules and cytokines to give all 3 signals

21
Q

Which cells are professional antigen presenting cells (APC’s) ?

A

Dendritic cells are the best antigen presenting cells

-Macrophages and B cells do it to

22
Q

Describe the process of MCH II antigen presentation?

A
  1. Phagocytosis of pathgen by antigen presenting cells
  2. Pathogen is chopped up by phagolysosomes enzymes
  3. Antigens are loaded onto the MCH II in the phagolysosome
  4. Activates CD4+ helper T cells
23
Q

What is cross-presentation of dendritic cells?

A

Cross presentation of dendritic cells is how dendritic cells can also present antigens on the MCH I molecule, meaning they can activate both helper and cytotoxic T cells

24
Q

Describe the costimulation signal needed to activate T cells

A

B7 family molecules activate CD28 on T cells

-boosts the strength of the activation signal

25
Q

Describe the cytokine signal need to T cell activation

A

Cytokines are released by the dendritic cell. The type of cytokine released decides the mechanism that leads to the killing of that organism

26
Q

How are antigens broken down and presented?

A

Large protein antigens are broken down into small epitopes (pieces) of the antigen
Epitopes are bound to the antigen binding groove in Human Leukocyte Antigens (HLA) encoded by MHC genes

27
Q

What is an epitope?

A

A small part of an antigen that is recognized by the immune system

28
Q

What is the function on NK cells?

A

Kill virally infected cells and foreign cells such as early cancer cells

29
Q

How do NK cells know which cells to kill?

A

Depends on the balance of activating and stimulating ligands on the surface of cells
-Cancer and infected cells have more activating ligands which activates the NK cell to kill it

30
Q

How do NK cells kill other cells?

A

Release of cytotoxic granules containing perforin and granzymes, which leads to lysis of the cell

31
Q

What cytokines do NK cells release?

A

Once it has killed an infected cell, it releases cytokines such as IFNy and IFNa which act on cells like macrophages and dendritic cells to increase immune response

32
Q

What is the function of a dendritic cell?

A

They are antigen presenting cells

-They process antigenic material and present it on the cell surface to T cells

33
Q

What is the function of T helper cells?

A

See antigens presented on MHC II

-produces cytokines to activate other immune cells

34
Q

What are the different types of T helper cells?

A

Th1 , Th2, Th17, Tfh, Treg

35
Q

What is a Tfh cell?

A

A T follicular helper cell

-activates and matures B cells

36
Q

What is a Treg cell?

A

Regulatory T cells

-Supress other effector T cells

37
Q

What is the function of Th1 cells and what cytokines does it secrete?

A

Th1 cells activate macrophages

-secrete IFNy

38
Q

What is the function of Th2 cells and what cytokines does it secrete?

A

Th2 cells activate eosinophils and mast cells. Alternative macrophage activation
-secrete IL-4, IL-5, IL-13

39
Q

What is the function of Th17 cells and what cytokines does it secrete?

A

Th17 cells enhance neutrophil response

-secrete IL-17, IL-22

40
Q

What is the function of Tfh cells and what cytokines does it secrete?

A

Tfh cells activate and mature B cells

-Secrete IL-21 ( and IL-4 or IFNy)

41
Q

What is the function of Treg cells and what cytokines does it secrete?

A

Treg cells supress other effector T cells

-Secrete IL-10, TGFb

Immunology (10 decks)

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