Phylogenetically conserved antigen on nerve cells and lymphocytes resembles myelin-associated glycoprotein

The HNK-1 (Leu 7) and NC-1 monoclonal antibodies, raised against a human T-cell line and against nerve cells of quail embryos, respectively, have been shown to bind to a shared epitope present on the surface of human large granular lymphocytes and on nerve cells in species ranging from amphibians to humans. We demonstrate that a related antigen is also expressed on the lymphocyte surface in the avian central lymphoid organs, thymus and bursa, and in the spleen during embryonic and adult life. The expression of the HNK-1/NC-1-reactive determinant differs remarkably in the bursal and thymic compartments, antigen expression being stabilized at a high level early in development of the bursa, whereas its expression fluctuates in the thymus. The material immunoprecipitated from bursal and thymic lymphocytes by the HNK-1/NC-1 antibodies exhibits the same relative molecular mass as myelin-associated glycoprotein, which is one of the molecules recognized by these antibodies in the nervous system. Together with the observation that an antiserum reactive with the protein part of chicken myelin-associated glycoprotein detects similar material in membrane extracts of HNK-1/NC-1-positive thymocytes, this suggests that a molecule sharing structural analogies with this nerve cell component is expressed on cells of the immune system.