[The role of semaphorin family in immune systems]

Semaphorins are soluble and membrane-bound proteins originally identified as axonal growth cone-collapsing guidance molecules which are involved in the development of the neuronal system. Recently, cumulative evidences indicate that several semaphorins also participate in various phases of immune responses, both physiological and pathological. They are so-called 'immune semaphorins' such as sema3A, 3E, 4A, 4D, 6D, and 7A. Some semaphorins regulate immune cell activation or differentiation, whereas others navigate the trafficking of immune cells. Moreover, Plexin family members and neuropilins are the most representative receptors for semaphorins, which have cell type-specific patterns of expression and are involved in multiple signaling responses. At present, semaphorins and their receptors are considered to be potential diagnostic and therapeutic targets for many kinds of diseases. Here, we review the current knowledge of the function of semaphorins and their corresponding receptors in immune systems, which is especially focused on class3 and class4 semaphorins.