Abstract
The major glycoprotein (gp70) of murine leukemia virus occurs free of virus in the serum and body fluids of certain strains of mice. These glycoproteins were isolated from New Zealand Black mouse (NZB) ascites fluid and from AKR and New Zealand White mouse (NZW) serum by immunoaffinity chromatography and were compared by immunological tests and peptide mapping. Glycoproteins gp70-NZB and gp70-NZW were indistinguishable by all criteria tested and were more closely related to gp70 from Moloney leukemia virus than was gp70-AKR.