Semaphorins are primarily known for the important role they play in the guidance of growth cones during neuronal development. There is evidence, however, that semaphorins are expressed outside the nervous system as well, suggesting a wider scope for semaphorin function. The overall objective of our study is to identify the functions of semaphorins outside central nervous system especially in T cell development. Some of the 20 semaphorins have been shown to have extra-neural functions that include (for different semaphorins) bone differentiation, promotion of B-cell survival and aggregation, and activation of T-cells. Apart from central nervous system statement of most semaphorins, one semaphorin (CD 100) has transcripts in T cells, B cells, neutrophils, monocytes and granulocytes. EST analysis suggests that other semaphorins are expressed in lymphoid tissues such as thymus, spleen, tonsil, and the interfollicular areas and germinal centers of lymph nodes.

Semaphorins have been related to several cell survival mechanisms, immunosuppression and promotion of cell death resistance. in preliminary studies our lab found that viral semaphorins inhibit the migration of human T cells and human SEMA3A can inhibit migration of human neutrophils.