 They not only guide axons in development, but also have major roles in immune function (classes 4, 6, and 7) and the development of bones.Class 3 semaphorins are one of the most versatile semaphorin classes, in which Sema3a is the most studied.During development, semaphorins and their receptors may be involved in the sorting of pools of motor neurons and the modulation of pathfinding for afferent and efferent axons from and to these pools.