Question

Describe the zones of a lymphnode as to their function and how the lymphnode architecture helps detect infectious agents. Mention the location of the T and B lymphocyte, macrophages and dendritic cells in the lymphnode, and describe the function of a follicle and germinal center and high endothelial venules.

Answer 1

Lymph node, is a bean-shaped masses of lymphoid tissue enclosed by a capsule of connective tissue that occur in association with the lymphatic vessels.

Each lymph node is divided into two regions, the capsule and the cortex.The capsule is an outer layer of connective tissue which project internally to form trabeculae. The cortex is further divided into two functional areas: the outer cortex and inner cortex which surround an inner medulla, which consists primarily of activated antibody-secreting plasma cells.

Infections that spread to lymph nodes are usually caused by bacteria, a virus, or a fungus. The lymph nodes filter the fluid and release it back into the bloodstream together with salts and protein and they also contain immune cells that to fight infection by attacking the germs or infectious agents that the body's lymph fluid has collected. lymph nodes contain lymphocytes, which has B cells and T cells. They circulate through the bloodstream and enter and reside in lymph nodes.B cells produce antibodies which has a single predetermined target, an antigen, that it can bind to. These circulate throughout the bloodstream and find the target, the antibodies bind to it and stimulate an immune response.

The lymph nodes may swell when a person has a temporary infection.

B cells are mainly found inthe outer cortex in lymphoid follicles and T cells and dendritic cells are mainly found  in the paracortex. The regions where there are few cells within the meshwork are known as lymph sinus and it is lined by reticular cells, fibroblasts and fixed macrophages.

The lymph follicles contain B and T cells , which are important agents of immunity. They provide immunity or protection from infectious agents.

Germinal centre are a site where B cells become activated, proliferate, switch to Ig class, and increase affinity for the antigen by somatic hypermutation during a normal immune response to infection.

High Endothelial Venules (HEVs) are specialized blood vessels which support the migration of naive lymphocytes from the bloodstream into secondary lymphoid organs.