The CD100-CD72 interaction: a novel mechanism of immune regulation

CD100 is a 150 kDa transmembrane protein that belongs to the semaphorin fam ily. Many members of the semaphorin family are known to play crucial roles in axon guidance, acting as chemorepulsive factors during neuronal developm ent. CD100 is the first member of the semaphorin family for which crucial r oles in the immune system have been identified. Although plexin-B1 has been shown to be the receptor for CD100 in nonlymphoid tissues, CD72 functions as its receptor in lymphoid tissues. CD100 plays a nonredundant role in the immune response by a unique mechanism that involves switching off the nega tive signals mediated by CD72.