Role of Thymus in T-Cell Maturation and Selection

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What is the key role of the thymus in T-cell maturation?

Proliferation of T lymphocytes in the medulla

Expression of CD4, CD8, and a TCR in arriving T lymphoblasts

Selective removal of T cells reactive against self-antigens (correct)

Production of cytokines for T-cell maturation

Where in the thymus do mature T lymphocytes exit by passing through the walls of venules and efferent lymphatics?

Cortex

Microvasculature

Medulla (correct)

Tight layer of TECs

What is the outcome of positive selection in the thymus?

Binding to MHC molecule results in cell death

Recognition of self-antigens promotes proliferation

Increased expression of CD4 and CD8 (correct)

Survival dependent on not recognizing self-antigen

In the thymic medulla, what determines the survival of pre-T lymphocytes?

Recognition of self-antigens Signup and view all the answers

Which cells within the thymus present MHC molecules with antigens to pre-T lymphocytes in the cortex?

Cortical epithelial cells Signup and view all the answers

What happens to pre-T lymphocytes in the thymus that recognize self-antigens during negative selection?

They die by apoptosis Signup and view all the answers

What is the main function of squamous thymic epithelial cells (TECs) in the cortex of the thymus?

Forming a layer that surrounds the microvasculature to create an isolated cortical compartment Signup and view all the answers

What prevents unregulated exposure of thymocytes to antigens in the thymus?

Blood-thymus barrier formed by squamous TECs Signup and view all the answers

What is the role of stellate TECs in the thymus?

Forming a cytoreticulum for attachment of macrophages and developing lymphocytes Signup and view all the answers

Which cell type in the thymus express MHC class II molecules and secrete cytokines for T-cell development?

Stellate TECs Signup and view all the answers

What is the function of the cortical epithelial cells in the thymus during T-cell maturation?

Providing a microenvironment for positive and negative selection of T cells Signup and view all the answers

Which feature distinguishes squamous thymic epithelial cells (TECs) from stellate TECs in the thymus?

Contain keratin tonofilaments joined by desmosomes Signup and view all the answers

What is the main function of Hassall corpuscles in the thymic medulla?

Secrete cytokines that control activity of local dendritic cells Signup and view all the answers

Which cell type is less densely packed in the thymic medulla compared to the cortex?

Dendritic cells Signup and view all the answers

What is the primary role of squamous cortical TECs in the thymus?

Form a functional corticomedullary barrier Signup and view all the answers

What is the unique feature of thymic corpuscles in the medulla?

Secrete factors promoting development of regulatory T cells Signup and view all the answers

Which structure forms a boundary between the cortex and medulla in the thymus?

Cytoreticulum Signup and view all the answers

What characterizes secondary nodules in lymphoid organs?

Larger, more euchromatic cells centrally Signup and view all the answers

Role of Thymus in T-Cell Maturation and Selection

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