Description
CD134 (OX40) is a T cell activation antigen structurally belonging to a lymphocyte-specific subgroup of the nerve growth factor and tumor necrosis factor receptor superfamily, which also includes the T cell antigen CD27, B cell antigen CD40, FAS antigen and the T cell activation antigen 4-1BB. The human CD134 protein is expressed only on activated CD4+ T blasts, and its ligand has been identified as gp34. Interactions between CD134 and its ligand in vivo are necessary for the differentiation of activated B cells into highly immunoglobulin-producing cells, however not involved in other pathways of antigen-driven differentiation of B cells such as development of memory cells in the germinal centers. In addition, the CD134 and gp34 system directly mediate adhesion of activated T cells to vascular endothelial cells, and contribute to growth stimulation of the virus-infected T cells