Journal of Neuroimmunology, 11 (1986) 67-86 67 Elsevier JNI 00336 Neuronal Differentiation of Cloned Human Teratoma Cells in Response to Retinoic Acid in Vitro Michael Webb 1,,, Christopher Graham 2 and Frank Walsh 1 I Institute of Neurology, Queen Square, London WC1, and 2 Zoology Department, University of Oxford, South Parks Road, Oxford (U.K.) (Received 15 May, 1985) (Accepted 17 July, 1985) Summaff We have analysed immunocytochemically the differentiation in vitro of clones of the human teratoma cell line Tera-2. The proliferating stem cells expressed Thy-1 and N-CAM/D2-CAM antigens. On treatment with 5 × 10 -5 M retinoic acid in either monolayer or aggregate cultures they began to express receptors for tetanus toxin and McAb A2B5. Three weeks after initiating retinoic acid treatment, the cultures contained a variety of cell morphologies, including about 3% of cells with a neuron-like morphology. These cells were reactive with tetanus toxin, McAb A2B5, and antibodies against Thy-1 and N-CAM/D2-CAM. They also expressed 55 000 and 210 000 Da neurofilament subunits. Key words: Differentiation- Human teratoma- Immunocytochemistry- Neurons Introduction During early development, the cells which will form the central and peripheral nervous systems arise respectively from 2 embryonic structures, the neural tube and the neural plate. Although both develop from the cells of these primitive structures, little is known of the lineage relationships of neurons and the major glial cell types * To whom correspondence should be addressed. Present address: Sandoz Institute for Medical Research, 5 Gower Place, London WC1E 6BN (U.K.). Abbreviations: McAb, monoclonal antibody; PBS, phosphate-buffered saline; RA, retinoic acid. 0165-5728/86/$03.50 © 1986 Elsevier Science Publishers B.V. (Biomedical Division)