Recognizes a protein of 18-35kDa, identified as CD90 (also known as Thy1). CD90 is a member of the immunoglobulin superfamily. It may contribute to inhibition of proliferation/differentiation of hematopoietic stem cells and neuron memory formation in the CNS. It consists of a single Ig domain (112 amino acids; 25-35 kDa) inserted into the cell membrane via a GPI anchor. Expressed by hematopoietic stem cells and neurons in all species studied. Its highly expressed in connective tissue and various fibroblast and stromal cell lines, expressed on all thymocytes and peripheral T cells in mice, but in humans expressed only on small % fetal thymocytes, 10-40% of CD34+ cells in bone marrow, and <1% of CD3+CD4+ lymphocytes in peripheral circulation. It is also expressed by human lymph node HEV endothelium but not other endothelia. Lastly, it is expressed by a limited number of lymphoblastoid and leukemic cell lines.