Preparation of antisera to neurofilament protein from chicken brain and human sciatic nerve

Antigens isolated by hydroxyapatite chromatography from human sciatic nerve (SN1 protein) and from 8 M urea extracts of chicken brain were selectively localized by immunofluorescence to neurofibrils in rat and chicken CNS. Absorption of the antisera with SN1 protein, chicken antigen or GFA protein abolished the staining. Antisera raised against antigen isolated with the same procedure from buffer extracts of chicken brain stained both neurofibrils and glial fibrils by immunofluorescence. Neurofibrillary staining was selectively abolished by absorption of the antisera with SN1 protein. Antisera prepared against axonal preparations isolated from bovine white matter only stained astroglia and were thus undistinguishable from anti-GFA sera in this respect. The data suggested that the protein subunits of neurofilament and glial filaments, although difficult to separate in brain extracts by standard biochemical procedures and by subcellular fractionation in bovine white matter, still retain immunological specificity. In addition, the immunological cross reactivity between human and chicken antigens suggested that neurofilaments, as other constituents of the cytoskeleton such as microtubules and actin microfilaments, show a high degree of evolutionary stability.