Figure 2.

Semaphorins in immune cell interactions. Semaphorins are involved in various phases of immune cell responses. (a) During T-cell-mediated B-cell activation, engagement of CD72 by Sema4D induces dephosphorylation of CD72 and dissociation from SHP-1, which results in enhancement of BCR signals. Sema4D can also be cleaved proteolytically and function as a soluble form in an autocrine/paracrine manner. (b) Sema6D on T cells can activate DCs through plexin-A1. Sema4A on DCs binds to TIM-2 and activates T cells. (c) T-cell-mediated inflammatory responses require antigen–MHC class II–TCR interaction and CD40L–CD40 signals. However, the interaction between Sema7A and α1β1 integrin is also critical for activation of inflammatory cells such as macrophages.