Ab1 mAb Research Articles

Immunogold Labeling of Alzheimer Paired Helical Filaments with Ganglioside MAB A2B5

The ganglioside monoclonal antibody A2B5 has previously been used at the light microscopic level to label Alzheimer neurofibrillary tangles (NFTs). Light microscopic analysis, however, could not reveal whether the A2B5 antibody-labeled NFTs or membrane fragments associated with NFTs. Therefore, we used pre-embedding immunohistochemical electron microscopy to examine A2B5 labeling of NFT. We found that the A2B5 antibody does indeed label a NFT antigen associated with the paired helical filament (PHF) structure, while no significant labeling of membranes or membrane fragments was observed. However, no clear periodicity of the immunogold label on the PHF was found.

Antibodies against ganglioside GT3 in the sera of patients with type I diabetes mellitus.

Clinical and experimental data support the concept that type I diabetes mellitus results from autoimmune destruction of pancreatic beta cells. Although both proteins and glycolipids are targets of anti-islet cell antibodies, the Ag have not been purified or characterized. Previously, we observed that rat insulinoma (RIN) cell lines varied in their reactivity with both human antibodies and murine mAb A2B5, which binds to polysialo gangliosides. To determine the chemical basis of the varied immunoreactivity, we analyzed the glycosphingolipids of 5 RIN lines. Glycolipids bound by two mAb and by antibodies in the sera of type I diabetics were identified. The more immunoreactive RIN lines contained a much higher content of gangliosides and a higher proportion of complex gangliosides. The major gangliosides were GM3, GD3, and GT3. By high performance TLC immunostaining, we demonstrated that A2B5 and R2D6, an anti-beta cell murine mAb, bound most strongly to ganglioside GT3. The binding of human sera to gangliosides was analyzed by an ELISA assay. Although both normal and diabetic sera contained antibodies to various glycolipids, binding to GT3 was significantly elevated in 31 new-onset type I diabetics (p less than 0.001). The presence of the GT3 trisialosyl epitope on human islet cells was shown by immunofluorescent staining by both R2D6 and A2B5. These findings support previous suggestions that gangliosides play an important role in the immunopathology of type I diabetes, and identify for the first time a specific ganglioside Ag that is the target for autoantibodies in a subset of diabetic patients.