Thymus Development and Function

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Questions and Answers

What is the characteristic of thymic education in the thymus?

T cells acquire receptors for recognizing foreign antigens

T cells are eliminated due to non-functional TCR

T cells are activated to recognize self-antigens

T cells acquire 'tools of the trade' and ability to use them safely (correct)

What is the result of cells with non-functional TCR during thymic education?

They die due to lack of functional TCR (correct)

They undergo positive selection

They express CD4 and CD8

They recognize self-antigens

What is the primary function of thymic medullary epithelial cells (TMECs) during negative selection?

To express a variety of tissue-restricted antigens (correct)

To express CD4 and CD8

To activate T cells

To provide a microenvironment for T cell development

What is the outcome of T cells with high affinity for self-antigens during negative selection?

They are eliminated due to high affinity for self-antigens Signup and view all the answers

What is the characteristic of T cells that express CD4?

They recognize MHCII Signup and view all the answers

What is the process by which T cells acquire the ability to recognize self-MHC?

Positive selection for self-MHC Signup and view all the answers

What is the role of the thymic cortex in T cell development?

It is the site of thymic education Signup and view all the answers

What is the outcome of T cells that fail to undergo positive selection?

They die due to lack of functional TCR Signup and view all the answers

What is the primary function of CD4 T cells in the immune response?

Providing help to other immune cells Signup and view all the answers

What is the outcome of ineffective immune tolerance?

Autoimmunity and immunodeficiency Signup and view all the answers

What is the estimated number of possible TCR diversities generated by random events?

4.5x10^9 Signup and view all the answers

Which of the following cells is responsible for antigen presentation?

Dendritic cell Signup and view all the answers

What is the consequence of random TCR diversity?

Self-reactivity Signup and view all the answers

What is the function of CD8 T cells?

Killing infected cells Signup and view all the answers

What is the primary mechanism of generating TCR diversity?

Gene rearrangement Signup and view all the answers

What is the importance of self/non-self recognition?

To prevent autoreactivity Signup and view all the answers

Study Notes

Thymus Development and Function

Thymus develops from seeded bone marrow-derived precursors
Comprises multiple lobules with organized zones and specialized cell types
Essential for thymic education, where T cells acquire necessary tools for immune function

Thymic Education

T cells express functional TCR and accessory molecules (CD4 or CD8)
TCR genes are rearranged, and cells with non-functional TCR undergo apoptosis
Thymocytes learn to use TCR and CD4/CD8 safely, within the laws of MHC restriction

Positive Selection for Self-MHC

Thymocytes with affinity for self-MHC (MHC II or MHC I) are positively selected
Thymocytes without affinity for self-MHC undergo apoptosis

Negative Selection for Self-Reactive T Cells

Thymocytes with high affinity for self-antigens are eliminated to prevent autoimmunity
Low/moderate affinity thymocytes are allowed to mature, ensuring immune tolerance
Thymic medullary epithelial cells (TMECs) express tissue-restricted antigens, promoting immune tolerance

Importance of Self/Non-Self Recognition

Immune tolerance prevents autoreactivity while permitting appropriate anti-pathogen responses
Immune recognition ensures the adaptive immune response to foreign pathogens

Immune Tolerance and Immune Recognition

Key players in immune response include adaptive T cells, B cells, antigen-presenting cells, and innate immune cells
TCR diversity is generated by random gene rearrangement events, allowing for recognition of unseen pathogens
Random TCR diversity makes self-reactivity possible, highlighting the importance of immune tolerance