Roles of chemokines in thymopoiesis: redundancy and regulation

Thymus is the primary lymphoid organ involved in the development of thymocytes. Maturation related events of thymocytes within thymus, especially the widely discussed directional migration of thymocytes, is regulated by chemokines via chemokine receptors mediated signaling pathway. Multiple types of chemokines and chemokine receptors, as components of the network-interaction within thymic microenvironment, are involved in the thymopoiesis. It appears that these chemokines are functionally redundant and such phenomenon may be explained not only by the promiscuous, non-one-to-one matching between ligands-receptors within CXC or CC chemokine subfamily, but also by the various spatio-temporal expression patterns within different cell types and developmental stages. The redundancy and regulation of thymus expressed chemokines and chemokine receptors during thymocyte development are herein discussed.