Immunological Tolerance Flashcards Preview

POD Exam II > Immunological Tolerance > Flashcards

Flashcards in Immunological Tolerance Deck (13):
1

Tolerance:

Lack of an immune response when immune cells are exposed to antigen.

2

Central tolerance:

Elimination of self reactive T and B cells during development in the thymus or bone marrow.

3

Peripheral tolerance:

Mechanisms after the lymphocyte has left bone marrow or thymus and encounters self antigen.

4

When T cells show a high affinity for self-antigen in the thymus (2):

1. Deleted by apoptosis.
2. Survive and become regulatory T cells.

5

Transcription factor that regulates the expression of peripheral proteins in thymic tissue:

AIRE
- Autoimmune regulatory gene.

6

AIRE (3):

- Encodes a transcription factor that is expressed in the thymic medulla.
- Controls the expression of the thymic tissue restriction antigens.
- When defective --> autoimmunity.

7

Regulatory T cells (4):

- Most are CD4 T cells.
- Inhibit the activation of conventional CD4 and CD8 T cells and thus can prevent autoimmune and allergic disease.
- Produce IL-10 and CTLA-4.
- Express CD25 and transcription factor Foxp3.

8

When a self reactive T cell in the periphery encounters its self antigen it (3):

1. Anergy.
2. Deletion through apoptosis.
3. Suppression by T regulatory cells.

9

Anergy:

A state of immune unresponsiveness after antigen encounter.
- Absent co-stimulation.
- CTLA-4 binds and blocks B7 on the APC and delivers inhibitory signals to the T cell.

10

CTLA-4:

Always expressed on Treg cells and is expressed on cytotoxic T cells after their activation, serving as an "off switch".
- Has higher affinity for B7 than CD28.

11

Suppression by Tregs (4):

- Grow in response to IL-2.
- Produce cytokines IL-10 and TGF-beta.
- Express CTLA-4.
- Consume IL-2 so that is unavailable for effector T cells.

12

When developing B cells encounter self antigen in the bone marrow (2):

1. Edit receptors.
2. Deletion through apoptosis.

13

B cell receptor editing (3):

- Reactivate RAG genes.
- Resume Ig light chain recombination and make new light chain.
- Same heavy chain is expressed.