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Questions and Answers

What is the primary function of high endothelial venules (HEVs) in lymph nodes?

To store lymphocytes for future immune responses

To filter out pathogens from the lymph

To facilitate the entry of lymphocytes into the lymph node (correct)

To produce antibodies against invading pathogens

What is the order of lymph flow through a lymph node?

Afferent lymph vessel -> Intermediate sinuses -> Medullary sinuses -> Subcapsular sinus -> Efferent lymph vessel

Afferent lymph vessel -> Subcapsular sinus -> Intermediate sinuses -> Medullary sinuses -> Efferent lymph vessel (correct)

Afferent lymph vessel -> Medullary sinuses -> Intermediate sinuses -> Subcapsular sinus -> Efferent lymph vessel

Afferent lymph vessel -> Medullary sinuses -> Subcapsular sinus -> Efferent lymph vessel

What is the purpose of the paracortex in a lymph node?

To provide a site for antigen presentation and T cell activation (correct)

To filter out pathogens from the lymph

To facilitate the entry of lymphocytes into the lymph node

To store lymphocytes for future immune responses

What is the ultimate destination of lymphocytes that enter the lymph node?

The right lymphatic trunk and then the systemic circulation Signup and view all the answers

What is the function of the reticular fibers in the stroma of the lymph node?

To provide structural support to the lymph node Signup and view all the answers

What is the region between the cortex and medulla of a lymph node called?

Paracortex or inner/deep cortex Signup and view all the answers

What is the purpose of the afferent lymphatic vessels in relation to lymph nodes?

To transport lymphocytes into the lymph node Signup and view all the answers

What is the site where lymphocytes enter the lymph node through the wall of high endothelial venules (HEVs)?

Cortex Signup and view all the answers

What is the primary function of the lymphoid nodule/follicle?

To facilitate the proliferation and differentiation of lymphocytes Signup and view all the answers

What type of cells can be found in the germinal center of a lymphoid nodule/follicle?

Antigen-presenting macrophages and proliferating B lymphocytes Signup and view all the answers

What is the function of the marginal zone in a lymphoid nodule/follicle?

To store newly formed adult B cells and some T cells Signup and view all the answers

What cell type is responsible for 'education' of lymphocytes in the thymus?

Thymic epithelial cells Signup and view all the answers

What is the composition of the cortical region of the thymus?

Many immature T cells and some macrophages Signup and view all the answers

What structure separates the lobules of the thymus?

Connective tissue septa Signup and view all the answers

What is the primary function of the thymus?

To facilitate the development of T cells Signup and view all the answers

What type of cells can be found in the medulla of the thymus?

Not specified in the text Signup and view all the answers

What is the function of the strands of basal lamina in the splenic sinus?

To loop around the outside of the sinus Signup and view all the answers

What type of cells are found in the marginal zone of the spleen?

Macrophages, dendritic cells, and B lymphocytes Signup and view all the answers

What is the location of the marginal zone in the spleen?

Between the red and white pulp Signup and view all the answers

What is unique about the wall of the splenic sinuses?

It lacks a continuous basal lamina Signup and view all the answers

What is the source of blood in the marginal zone?

Central artery Signup and view all the answers

What happens to circulating T and B lymphocytes when they enter the spleen?

They enter the marginal zone before segregating to specific locations Signup and view all the answers

What is the primary function of FDCs in germinal centers?

Retention of antigen on the surface for prolonged periods Signup and view all the answers

What is the origin of FDCs?

Lymphoid Signup and view all the answers

What is the function of lymph nodes in regards to T cells?

Storage of memory T cells Signup and view all the answers

What is the purpose of high endothelial venules (HEVs) in lymph nodes?

Recirculation of lymphocytes Signup and view all the answers

What is the primary function of the spleen?

Filtration of blood Signup and view all the answers

What is the characteristic of FDCs that distinguishes them from macrophages?

Lack of MHC II molecules Signup and view all the answers

What is the site of lymphocyte recirculation?

Blood-lymph node-lymph-blood Signup and view all the answers

What is the function of macrophages in lymph nodes?

Phagocytosis of lymph components Signup and view all the answers

What is the primary function of dendritic cells?

To present antigens to T cells and initiate an immune response Signup and view all the answers

Where are dendritic cells primarily located?

In barrier tissues, including skin and mucosa Signup and view all the answers

What is the role of the C-C chemokine receptor 7 (CCR7) in dendritic cells?

To sense and migrate towards chemokines in the lymphoid tissue Signup and view all the answers

What is the difference between dendritic cells and macrophages in terms of their interaction with T cells?

Dendritic cells interact with naïve T cells, while macrophages interact with already-activated T cells Signup and view all the answers

What is the function of MHC proteins in dendritic cells?

To present antigens to T cells Signup and view all the answers

Where do dendritic cells typically present antigens to T cells?

In the lymph node Signup and view all the answers

What is unique about dendritic cells compared to other antigen-presenting cells?

They can present virtually any form of protein antigen on both MHC I and MHC II Signup and view all the answers

What type of cells are found in the bone marrow?

T cells, B cells, and NK cells Signup and view all the answers

Study Notes

Structure of a Lymph Node

Lymphocytes enter lymph nodes through afferent lymphatic vessels and high endothelial venules (HEVs) in the deep cortex.
Lymphocytes move to the T and B domains of the lymph node, or pass through the parenchyma and leave via an efferent lymphatic vessel.
The direction of lymph flow in a lymph node is: afferent lymph vessel → subcapsular sinus → intermediate (radial or trabecular) sinuses → medullary sinuses → efferent lymph vessel.

Lymph Node Function

Lymph nodes produce and maintain T and B cells, and store memory cells (especially Th cells).
They accumulate antigens delivered to lymph nodes to be recognized by T cells, inside and at the surface of APCs, thus initiating an immune response.
Lymph nodes filter lymph, phagocytose lymph components, and are a site for lymphocyte recirculation.

Dendritic Cells

Dendritic cells (DCs) are primarily located in barrier tissues, including skin and the mucosa of the gastrointestinal, respiratory, and genitourinary tracts.
DCs collect antigens and migrate from barrier locations to local lymph nodes, where they present antigens to "naïve" T cells in the T-cell zone.
DCs are responsible for priming naïve T cells to become activated during the initiation of an adaptive immune response.

Thymus

The thymus is a primary lymphatic and endocrine organ responsible for T cell development.
It is made of many pseudolobules, each with an outer cortex and an inner medulla.
The outer cortex contains many immature T cells, which undergo selection or "education" of lymphocytes.

Follicular Dendritic Cells (FDCs)

FDCs are found in germinal centers and have multiple, thin, hair-like branching cytoplasmic processes that interdigitate between B cells.
Antigen–antibody complexes adhere to the dendritic cytoplasmic processes by means of the antibody’s Fc receptors, allowing FDCs to retain antigen on their surface for weeks, months, or years.

Spleen

The spleen is a large, dark-red, oval, highly vascular lymphatic organ located to the left of the stomach below the diaphragm.
It is organized into areas of red pulp and white pulp.
The marginal zone of the spleen is a sinusoidal region between the red and white pulp, rich in macrophages and other APCs.

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