The antigen recognized by the monoclonal antibody 3CB2 (3CB2-Ag and 3CB2-mAb, respectively) is expressed in radial glia and astrocytes of the developing and adult central nervous system (CNS) of vertebrates, as well as in CNS stem cells. The purpose of this investigation was the identification of 3CB2-Ag and the study of its expression in the adult human retina. 3CB2-Ag was identified as vimentin by one- and two-dimensional polyacrylamide gel electrophoresis, immunoblotting and proteomic analysis applied to protein extracts from the human glial cell line U-87 (derived from a malignant astrocytoma). 3CB2-mAb recognized three vimentin isoforms in glial cell lines. 3CB2-Ag expression in the human retina occurred in Müller cells, astrocytes, some blood vessels and cells in the horizontal cell layer, as determined by immunoprecipitation and immunofluorescence. Three populations of astrocytes were distinguishable by double labeling immunohistochemistry: vimentin+/GFAP+, vimentin-/GFAP+ and vimentin+/GFAP-. Our main conclusions are: 1) 3CB2-Ag is vimentin; 2) vimentin isoforms are differentially expressed in normal and transformed astrocytes; 3) human retinal astrocytes are molecularly heterogeneous; 4) 3CB2-mAb is a valuable tool to study vimentin expression and its function in the human retina.

Supported by Grant numbers BFI2002-04481-C02-02, BFU2005-08786-C02-01 (to CP) and BMC2003-07751-C03-01 and SAF2004-08570-C02-02 (to EjdlR) from the Dirección General de Investigación, Ministerio de Educación y Ciencia of Spain, and 08.1/0029/1999 (to CP and EjdlR) from the Comunidad de Madrid, Spain