Lymphatic System Lecture Quiz

Dendritic cells are antigen-presenting cells that play a crucial role in activating T cells in the immune response. They are primarily found in T cell-rich areas such as lymph nodes, spleen, and other secondary lymphoid organs. These areas are where T cells are most likely to encounter antigens and initiate an immune response. Therefore, it is true that dendritic cells are found in T cell-rich areas.

The statement is false because a person can live without a spleen. While the spleen plays important roles in filtering blood and fighting infections, it is not essential for survival. Other organs in the body can compensate for its functions. In some cases, the spleen may need to be removed due to injury or disease, and individuals can still lead normal lives without it.

Adipose tissue refers to fat tissue, which is not typically found in the thymus. The thymus is a gland responsible for the development and maturation of immune cells called T-lymphocytes. As a person grows older, the thymus gradually decreases in size and is replaced by adipose tissue. Therefore, it is incorrect to say that a person will have more adipose tissue in their thymus when they are a child compared to when they are an adult.

Peyer's patches are located in the ileum, which is the final section of the small intestine. These patches are part of the lymphatic system and play a crucial role in immune function. They contain specialized immune cells called lymphocytes that help protect the body against harmful pathogens and bacteria that may enter the digestive system. The ileum is specifically chosen as the location for Peyer's patches because it is where most of the nutrient absorption takes place, making it an ideal site for immune surveillance and defense.

The Periarterial Lymphatic Sheath (PALS) is a region in the spleen where lymphocytes are found. T cells are a type of lymphocyte that play a crucial role in cell-mediated immunity. Therefore, it is expected to find T cells near the PALS as they are involved in immune responses.

Wiskott-Aldrich Syndrome:
X-linked defect caused by numerous mutations in the X chromosome especially the Wiskott Aldrich syndrome protein (WASP) expressed in lymphocytes and megakaryocytes

Based on the given options, the most likely diagnosis for the patient is Hodgkin Lymphoma. Neutropenia refers to a low count of neutrophils, which is not specified in the question. Sickle-Cell Anemia is a genetic disorder characterized by abnormal red blood cells, which is not mentioned in the question. Elliptocytosis is a condition where red blood cells have an elliptical shape, which is also not mentioned in the question. Therefore, Hodgkin Lymphoma is the most reasonable choice based on the given information.

IgM is the antibody most associated with the primary immune response. During the primary immune response, the body produces IgM antibodies as the first line of defense against pathogens. IgM is the largest antibody and is produced in large quantities initially to neutralize and eliminate the invading pathogens. It activates complement proteins to enhance the immune response and is crucial for clearing the infection during the early stages. As the immune response progresses, other antibodies such as IgG, IgD, and IgE may also be produced, but IgM is the primary antibody involved in the initial immune response.

The reticular meshwork and cells in lymphatic tissues are derived from the mesenchyme. Mesenchyme is a type of embryonic connective tissue that gives rise to various cell types, including fibroblasts, which are responsible for producing the reticular fibers that make up the meshwork in lymphatic tissues. This process occurs during embryonic development when mesenchymal cells differentiate into specialized cell types to form the lymphatic system. Myeloid cells and erythroid cells are not involved in the development of the reticular meshwork and cells in lymphatic tissues. PPSC (presumptive pluripotent stem cell) is not relevant to this context.

The MHC gene is located on chromosome 6.

Lymph nodules or follicles are small structures found in the lymphatic system that contain immune cells. Reticular cells are specialized cells found in lymphoid tissues that produce various types of collagen. Type III collagen, also known as reticular collagen, is primarily produced by reticular cells. It forms a network of fibers that provide structural support to lymphoid tissues, helping to maintain their shape and organization. Therefore, it is logical to conclude that reticular cells produce type III collagen in lymph nodules/follicles.

3 types of sinuses in lymph nodes:
Subcapsular or cortical sinuses: between node capsule and cortical lymphocytes. Site of afferent lymph vessel drainage
Trabecular sinuses: originate on cortical sinus, travel along trabeculae and drain in medullary sinuses
Medullary sinuses: in the medulla of lymph nodes

Type I:
Boundary of connective tissue cortex and trabeculae
Surround adventitia of cortical blood vessels
Separate thymic parenchyma from connective tissue  separates developing T cells from connective tissue
Type II:
In the cortex
Rich in desmosomes (maculae adherens)
Separate and compartmentalize cortex into isolated areas for the developing T cells
Express MHC I and MCH II molecules  thymic cell education
Type III:
Boundary of cortex and medulla
Occluding junctions
Functional barrier between cortex and medulla
Have MHC I and MHC II molecules
Type IV:
Close to type III cells
Tight junctions
Help create barrier at corticomedullary junction
Type V:
Contain desmosomes
Framework and compartmentalization of medulla
Type VI:
Form Hassall’s corpuscles  isolated masses  flattened nuclei
Desmosomes
Produces IL-4 and IL-7  thymic differentiation and education of T cells

There are six types of epithelioreticular cells.

Type VI epithelioreticular cells form Hassall's corpuscles. Hassall's corpuscles are found in the thymus gland and are composed of concentric layers of epithelial cells. These cells are derived from the endoderm and play a role in the maturation of T-cells. Type VI epithelioreticular cells are responsible for the production of keratin and the formation of the characteristic concentric layers seen in Hassall's corpuscles.

DiGeroge Syndrome:
Caused by pinpoint deletion in chromosome 22  defective development of 3rd and 4th pharyngeal pouches  Absent thymus, abnormal cardiac development and defective parathyroid glands
Pts with heart defects, hypocalcemia and recurrent viral, bacterial and fungal infections  NO T lymphocytes in the most severe form
Some patients may have a rudimentary thymus
Many patients die in early childhood due to uncontrollable infections  no cell mediated immunity

Th2 cells interact with all of the cells listed except for B cells. Th2 cells are a subset of T helper cells that play a crucial role in regulating immune responses, particularly in allergic reactions and defense against parasites. They primarily interact with B cells, cytotoxic T cells, and macrophages to coordinate the immune response. Th2 cells help activate B cells, which then produce antibodies to fight against pathogens. They also interact with cytotoxic T cells and macrophages to enhance their functions. However, Th2 cells do not directly interact with NK cells, which are part of the innate immune system and primarily involved in killing virus-infected cells and tumor cells.

The spleen is not a central lymphatic organ because it is not involved in the production and maturation of lymphocytes. Instead, the spleen is a secondary lymphoid organ that filters the blood and removes old or damaged red blood cells. The central lymphatic organs include the bone marrow and thymus, which are responsible for the production and maturation of lymphocytes. GALT (Gut-Associated Lymphoid Tissue) is also considered a central lymphatic organ as it plays a crucial role in immune responses in the gastrointestinal tract.