T follicular helper cells (TFH cells) provides a helper function to B cells. It is one of the most important subsets of effector T cells in lymphoid tissues. The features of TFH cells include chemokine receptor expression (CXCR5), location/migration (B cell follicles), and function (B cell help). TFH cells produce a "helper" cytokine-IL-21, which can stimulate B cells to differentiate into Ab-forming cells through IL-21R. Dysregulation of TFH cell function likely contributes to the pathogenesis of immune-related diseases. In this article, the discovery of CXCR5 and TFH cells, origin of TFH cells, cytokines related with TFH cell function, migration and location of TFH effector cells and memory cells as well as dysregulation of TFH cell function and related diseases were reviewed.