Anti-myelin associated glycoprotein antibodies: variability in patterns ofIgM binding to peripheral nerve

We previously found that serums with anti-sulfatide antibodies have several different patterns of binding to neural tissue. In this study, we asked wh ether serums with anti-myelin associated glycoprotein (MAG) antibodies also have similar variations in patterns of tissue binding. We examined binding to peripheral nerve in 49 serums with IgM anti-MAG antibodies and 13 serum s with IgM anti-sulfoglucuronyl paragloboside (SGPG) antibodies but no MAG binding. We correlated patterns of binding with titers of IgM binding to MA G and SGPG measured by ELISA methods. Our results show that IgM in most ant i-MAG serums stained areas of non-compact myelin, including the periaxonal and outer myelin membranes and Schmidt-Lanterman incisures. However, other patterns included IgM binding to areas of compact myelin and to non-myelin structures including axons and endoneurial macrophages. IgM in anti-SGPG se rums bound to axons or macrophages, but rarely to myelin-related structures . A total of 11/62 (18%) of serums had I-M binding to axons, six with anti- MAG antibodies and five with anti-SGPG antibodies. The majority of these se rums (73%) had SGPG titers greater than MAG titers when measured by ELISA. We conclude that anti-MAG serums have several different binding patterns to neural tissue, including axonal binding, especially when anti-MAG antibodi es cross-react with SGPG. These different binding patterns may relate to th e ability of anti-MAG serum IgM to bind both MAG and SGPG or to other molec ules with a sulfated glucuronic acid epitope that are present in peripheral nerve. (C) 2001 Elsevier Science B.V. All rights reserved.