Stromal cells as coordinators of adaptive immune response and immunological memory

The Greek term stroma literally means in translation mattress, covering or bed. In the medical context this describes the connective tissue framework of an organ which is composed of the stromal cells and the extracellular matrix components which are produced by these cells. According to the original definition stromal cells have a non-hematopoietic origin and adherently grow in cell culture. Nowadays the term is used to cover a heterogeneous group of connective tissue cells of mesenchymal origin which includes fibroblasts, reticular stromal cells and endothelial cells as well as tissue-specific connective tissue cells, such as osteoblasts and adipocytes. Because the stromal cells in the various tissues are very different with respect to morphology and functional characteristics, the manifold aspects of the individual stromal cell populations are now just beginning to be understood. This article presents a summary of new knowledge on the various functions of stromal cells in the immune response.