IDENTIFICATION AND CHARACTERIZATION OF DIFFERENTIATION-DEPENDENT SCHWANN-CELL SURFACE-ANTIGENS BY NOVEL MONOCLONAL-ANTIBODIES - INTRODUCTION OF A MARKER COMMON TO THE NON-MYELIN-FORMING PHENOTYPE

In an attempt to identify and characterize novel Schwann cell surface molecules with putative functions during development, maintenance, and regeneration of the peripheral nervous system (PNS), we have produced monoclonal antibodies against viable neonatal rat Schwann cells. Usin g a sensitive live cell ELISA protocol, three monoclonal antibodies re active with cultured Schwann cells, designated 27B10, 26F2, and 27C7 w ere isolated. The 27B10 and 26F2 antibodies specifically labelled fors kolin-stimulated secondary Schwann cells in vitro as determined by liv e cell ELISA implying that the expression of the antigens in situ is r egulated by axonal contact. The observation that the antigens seemed t o be associated with both Schwann cell phenotypes clearly discriminate d them from the well characterized myelin proteins as well as from mol ecules known to be confined to the non-myelin-forming phenotype. Inter estingly, both antigens were found to be concentrated at the nodes of Ranvier. Further studies therefore have to show whether the identified antigens share structural or functional homology with adhesion or cha nnel molecules, which display a similar distribution. Following transe ction of the adult sciatic nerve, the 26F2 antigen was rapidly down-re gulated in the distal nerve stump. The 27C7 antibody reacted with an 8 0 kDa cell surface molecule common to non-myelin-forming Schwann cells . No differences in expression of the antigen between forskolin-treate d and untreated Schwann cells in vitro were found, suggesting that the antigen is expressed independently from axonal contact. Two weeks aft er nerve transection in the absence of myelinating Schwann cells, the antigen was associated with S-100-positive Schwann cells of the distal nerve stump. The antigen was found to be expressed also by non-neuron al tissues, the level of the protein declined towards the adult stage. Comparison of the 27C7 antigen with previously described marker molec ules suggests that we have identified a novel Schwann cell surface ant igen of the non-myelin-forming phenotype. (C) 1997 Wiley-Liss, Inc.