Stromal cell heterogeneity in lymphoid organs.

Although the role of stromal cells has not been clearly defined, these cells have been described as forming the extracellular matrix in all lymphoid organs. Their important role in facilitating the development of immune cells in the thymus and bone marrow has long been known. In contrast, stromal cells have been found in secondary lymphoid organs and it has been shown that they are important mediators during organogenesis. More recently, their important function in the guidance and survival of immune cells has been documented. Here, we describe the important role of stromal cells within secondary lymphoid organs and highlight the fact that the immunological function of stromal cells is site-specific and unique in each lymphoid organ.