Regulation of lymphocytes

Question 1

Why is lymphocyte regulation required?

Answer 1

To prevent responses against self cells

Question 2

What is autoimmunity?

Answer 2

An immune response against self antigens, attacking self cells as they would a pathogen

Question 3

What is allergy?

Answer 3

A harmful immune response to non-infectious antigens that cause tissue damage and disease

Question 4

What mediates allergy?

Answer 4

Mediated by antibody (IgE) and mast cells - acute anaphylactic shock
Or by T cells - delayed type hypersensitivity

Question 5

What is hypercytokinemia?

Answer 5

Where too much immune response occurs and often happens in a positive feedback loop
Triggered by pathogens entering wrong compartmen(sepsis) or failure to regulate response to correct level

Question 6

What is the 3 signal model for naive T cells?

Answer 6

1. Antigen recognition
2. Co-stimulation: Where the T cell and the activating cell engage with molecules on the T cell surface and stimulate the signalling cascade
3. Cytokine release: Molecules produced by one cell activate another cell
   All 3 signals have to be met in order for a response to be induced

Question 7

What are the 3 phases of cell mediated immunity?

Answer 7

1. Cell infected dendritic cell collects material
2. MHC:peptide T cell receptor interaction
3. Naive T cell becomes effector and sees MHC:peptide on infected cells and performs it’s function

Question 8

What occurs at the end of an immune response?

Answer 8

Resolution - No tissue damage and phagocytosis of cell debris by macrophages
OR
Repair - Healing with scar tissue and regeneration, fibroblast and collagen synthesis
OR
Chronic inflammation - Disease never clears and inflammation is present at all times and causes the immune reaction to constantly act

Question 9

What is the problem with chronic diseases?

Answer 9

Over time the T cells start to deactivate themselves by actively putting suppressors on their surface
This can slowly begin to deactivate the immune response and lead to other diseases elsewhere in the body

Question 10

What is immunological tolerance?

Answer 10

Exposure of a lymphocyte to an antigen and becoming unresponsive to that cell antigen

Question 11

What are the benefits of immunological tolerance?

Answer 11

It allows for self tolerance

Potentially can revert self attacking lymphocytes back into tolerated cells

Question 12

What is central tolerance?

Answer 12

Any self reactive cells are destroyed as they are made

Question 13

What is peripheral tolerance?

Answer 13

The destruction or control of any self reactive lymphocytes which have entered circulation

Question 14

How does central tolerance occur for B and T cells?

Answer 14

B cells - Produce their unique BCR
T cells - Tested if it binds to any self MHC, if not then it apoptoses
However if the T cell binds too strongly to the self MHC it is also destroyed - apoptosis
The ones that bind not too strongly to self MHC survive

Question 15

What is AIRE?

Answer 15

AutoImmune Regulator protein - a transcription factor that produces the entire repertoire of human proteins and loads it onto MHC molecules for the T cell to detect

Question 16

How does peripheral tolerance occur?

Answer 16

Anergy - If the T cell sees it’s MHC without costimulatory proteins, it becomes tolerated rather than activated (anergic)
Ignorance - Antigens may be too low a concentration to activate the T cells as the tissue may be immunologically pirivileged
Antigen induced cell death - Activation of the T cell results in apoptosis, ‘death ligand’ may be expressed

Question 17

What are the different types of CD4(T helper) cell and how do they work?

Answer 17

T helper 1 (Th1):
-Produce interferon gamma
-Boost intracellular immune response
T helper 2 (Th2):
-Produce IL4,5,13
-Boost anti-multicellular organism response
Follicular helper T cells:
-Produce IL21, resides in B follicles
-essential for generation of isotope switched antibodies
Th17 cells:
-Secret IL17 in autoimmune diseases such as arthiritis
- Important for control for bacteria
-NB other Th cells defined by cytokines e.g. Th9(IL9)
T regulatory cells(Treg):
-T cells that regulate the activation of effector functions of other T cells
-Natural and induced regulatory T cells
-necessary to maintain tolerance to self antigens
-Produce IL10

Question 18

What does IL-10 do?

Answer 18

It inhibits other T cells

Question 19

How is tolerance broken?

Answer 19

Some pathogens have antigens similar to self antigens, so in making B cells or T cells respond and attack the bacteria, they then detect the self antigen as well and attack it