Lymphocytes Development And Tolerance Flashcards
Where do T and B cells mature?
- T cells mature in the thymus.
- B cells mature in the bone marrow.
What is the role of the thymus in T cell development?
The thymus provides the microenvironment for T cell maturation, including positive and negative selection.
What is positive selection in T cell development?
The process that ensures T cells can recognize self-MHC molecules and survive.
What is negative selection in T cell development?
The removal of T cells that strongly bind self-antigens, preventing autoimmunity.
What are the three main mechanisms of B cell self-tolerance?
- Deletion (apoptosis of self-reactive B cells)
- Anergy (functional inactivation of self-reactive B cells)
- Receptor editing (rearrangement of light chain genes to change antigen specificity)
T cells undergo somatic recombination of TCR genes in the
thymus.
98% of thymocytes die during the
selection process in the thymus.
The autoimmune regulator (AIRE) in thymic medullary epithelial cells helps eliminate
self-reactive T cells.
Peripheral tolerance mechanisms exist to
eliminate self-reactive lymphocytes that escape central tolerance.
Allelic exclusion ensures each B or T cell expresses
only one antigen receptor specificity.
Positive selection occurs in the thymic medulla.
False – it occurs in the cortex.
Negative selection prevents autoimmunity by eliminating strongly self-reactive T cells.
True
B cells mature in the thymus.
False – they mature in the bone marrow.
AIRE allows thymic expression of peripheral self-antigens.
True
Thymic selection ensures that T cells recognize self-______________ but not self-______________.
MHC, antigens
The main site of B cell maturation is the ______________.
Bone marrow
The ______________ gene helps prevent autoimmunity by inducing the expression of peripheral antigens in the thymus.
AIRE
T cells that do not receive survival signals during positive selection undergo ______________.
Apoptosis
Which process ensures that T cells can recognize self-MHC?
a) Negative selection
b) Somatic hypermutation
c) Positive selection
d) Receptor editing
Answer: (c) Positive selection
Which mechanism prevents the activation of self-reactive B cells in the periphery?
a) Anergy
b) V(D)J recombination
c) Positive selection
d) Somatic recombination
Answer: (a) Anergy
What is the function of AIRE in the thymus?
a) Enhances T cell receptor diversity
b) Promotes peripheral tolerance
c) Expresses self-antigens for negative selection
d) Induces somatic hypermutation
Answer: (c) Expresses self-antigens for negative selection
A patient with DiGeorge syndrome lacks a thymus. What immune deficiency will they experience?
They will have a severe T cell deficiency, leading to increased susceptibility to infections.
A person develops an autoimmune disease due to a failure in negative selection. What type of cells escaped deletion?
Self-reactive T cells that recognize self-antigens too strongly.
A patient has an inherited mutation in the AIRE gene. What condition might they develop?
Autoimmune polyendocrinopathy syndrome (APS-1), due to failure in central tolerance.
Positive Selection:
The process that ensures T cells can recognize self-MHC and survive.
Negative Selection:
The elimination of strongly self-reactive T cells to prevent autoimmunity.
AIRE (Autoimmune Regulator):
A gene that promotes the expression of peripheral self-antigens in the thymus to eliminate autoreactive T cells.
Receptor Editing:
A mechanism in B cells that allows modification of antigen specificity to avoid self-reactivity.
Allelic Exclusion:
A process ensuring that each B or T cell expresses only one antigen receptor specificity.
