Immunohistochemical localisation of S–100 protein in brain

Abstract

IT is accepted that the brain-specific protein S–100 is associated predominantly with glial cells^1–5. More equivocal evidence exists to suggest a possible relationship of S–100 to neurones^3,6,7. Although well characterised antisera against S–100 have long been available⁸, few immunohistochemical studies of the location of S–100 antigen in brain have appeared. Two such studies have reported that S–100 is associated with neuronal elements^9,10 but in both cases the major glial fraction of S–100 does not appear to have been localised by the immunohistochemical techniques used. The recent study by Haglid et al.¹⁰ claimed to demonstrate that S–100 antigen is associated with the junctional membranes of brain synapses, and on this basis an ambitious theory of chemical events underlying “learning” has been proposed¹¹ in which S–100 is assigned a key role. We have now reinvestigated the distribution of S–100 in brain tissue using a specific antiserum against S–100 ( a generous gift from Dr L. Levine) which gave a positive response against rat brain extract at 1 : 1,400 dilution in complement fixation assay. The immunological properties of this antiserum have been described in detail by Kessler et al.¹².