Monoclonal antibody identifies a 63,000 dalton antigen found in all central neuronal cell bodies but in only a subset of axons in the leech.

The monoclonal antibody Lan3-8 binds to all the neuronal cell bodies in midbody, head, tail, and supraesophageal ganglia in the mud leech (Haemopis marmorata) and the medicinal leech (Hirudo medicinalis). In contrast to the general distribution of the antigen in cell bodies it is only found in a subset of axons, where electron microscopy suggests that it may be associated with a cytoskeletal filament system. Immunoblotting shows that the antibody binds to a 63,000 dalton band that is protease-sensitive. The same 63 kilodalton (kd)-antigen is found in all regions of the central nervous system, in proteins isolated from connectives (axons alone), and from hand-dissected identified cell types. The molecular weight and electron microscopic localization raised the possibility that this antigen is the core neurofilament protein, but the antigen does not comigrate with 67-kd intense coomassie blue band that binds another anti-intermediate filament antibody. The supraesophageal ganglia are known to have a different developmental or origin from the other structures in the leech central nervous system. Two-dimensional gel electrophoresis and silver staining show that, like the 63-kd antigen, many other proteins are very similar in these developmentally distinct neural structures.