Immunocytochemical and biochemical studies with the monoclonal antibody 69A1: similarities of the antigen with cell adhesion molecules L1, NILE and Ng-CAM.

We have previously raised a monoclonal antibody (69A1) which recognises a cell-surface antigen expressed on rat cerebellar neurons both in culture and in tissue sections of the developing cerebellum prior to postnatal day 17. In our current study we have undertaken a detailed analysis of the loss of labelling from the molecular layer of the cerebellum and show that this parallels the gradient of fibre maturation in this zone. This loss of labelling occurred in paraformaldehyde-fixed tissues but not in unfixed or acetone-fixed sections, suggesting it is the result of antigen modification rather than antigen loss. In cultures of dorsal root ganglia antibody 69A1 labelled neurones and some Schwann cells. Antigen 69A1 was immunoprecipitated from lysates of cultured cerebellar cells and appeared as two bands when separated by SDS-PAGE with apparent molecular weights of ca. 210 and 150 kDa. The antigen is distinct from N-CAM but shows similarities with the L1, nerve growth factor-inducible large external glycoprotein (NILE) and Ng-CAM group of cell adhesion molecules.