Lymph node stromal cells are essential to the structure and function of the lymph node. There are a number of different types of lymph node stromal cells which have a number of functions including: creating a tissue scaffold within lymph nodes for the support of hematopoietic cells; the release of small molecules that are chemical messengers that facilitate interactions between hematopoietic cells; the facilitation of the migration of hematopoietic cells; the presentation of antigens to immune cells at the initiation of the adaptive immune system; and the homeostasis of lymphocyte numbers. Stromal cells originate from multipotent mesenchymal stem cells.
Lymph nodes are enclosed in an external fibrous capsule and from this capsule, thin walls of sinew called trabeculae, penetrate into the lymph node, partially dividing it. Beneath the external capsule and along the courses of the trabeculae, are peritrabecular and subcapsular sinuses. These sinuses are cavities containing macrophages (specialised cells which help to keep the extracellular matrix in order).
The interior of the lymph node has two regions: the cortex and the medulla. In the cortex, lymphoid tissue is organized into nodules. In the nodules, T lymphocytes (cells which help to fight viruses) are located in the T cell zone. B lymphocytes (cells which help to fight certain bacteria) are located in the B cell follicle. The primary B cell follicle matures in germinal centers. In the medulla are hematopoietic cells (which contribute to the formation of the blood) and stromal cells.