T-cell antigen CD7, also known as CD7, is a type I transmembrane glycoprotein that is expressed on pluripotential hemapoietic cells, most human thymocytes and some peripheral blood T cells. The CD7 molecule is absent in a subset of human T cells under certain physiologic conditions. Thus an increase in CD7 negative T cells can be seen in some inflammatory skin disease. Recombinant human CD7 protein, fused to His-tag at N-terminus, was expressed in E.coli.