CD100, also known as Semaphorin 4D, is a homodimerizing type I transmembrane glycoprotein containing an extracellular semaphorin domain. It is expressed on most hematopoietic cells with the exception of immature bone marrow cells, erythrocytes and platelets. A 120 kDa soluble form is generated from the transmembrane form by proteolytic cascade following primary T and B cell activation. It seems CD100 acts through dampening CD72-mediated negative signaling. CD100 promotes angiogenesis, invasive growth, proliferation and anti-apoptosis of cancer cells in vitro. Higher expression levels of CD100 correlate with poor survival in soft tissue sarcoma patients.Specificity : The mouse monoclonal antibody 133-1C6 recognizes an extracellular epitope of CD100, an approximately 150 kDa (when reduced) semaphorin family member expressed mainly on lymphocytes, NK cells, monocytes/macrophages and granulocytes, but also on some non-hematopoietic cells.