Altered cell-surface protein(s), crossreactive with DNA, on spleen cells of autoimmune lupic mice

A murine monoclonal anti-DNA antibody, PME77, with specificity for double-stranded DNA, has previously been shown to react with a protein(s) present at the surface of such cells involved in lupus pathogenesis as human glomeruli, T and B lymphocytes, erythrocytes, and platelets. Mild elastase treatment of lymphoid cells from non-autoimmune (CBA/ca or BALB/c) mice releases a series of crossreactive polypeptides (34, 33, 17, 16, and 14 kDa) recognized by PME77. These polypeptides are not formed after treatment of the same cells with papain or trypsin. When lymphoid cells from autoimmune [MRL-lpr/lpr or (NZB X NZW)F1 B/W] mice are treated with elastase, trypsin, or papain, PME77 detects, in all supernatants, a single polypeptide of about 55 kDa. Antibodies present in the sera of autoimmune MRL-lpr/lpr and B/W mice and IgG eluted from kidneys of MRL-lpr/lpr mice react with the same polypeptides. Neither sera nor eluted IgG of normal BALB/c mice react with these polypeptides. These results suggest that an altered cell-surface protein(s), which we call LAMP [for lupus-associated membrane protein(s)], may be involved in lupus pathogenesis.