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IgG antibodies reacting with the GM3-comigrating band extracted from pooled AIDS lymphocytes were detected in 33.3% of AIDS patients sera, in 8% of asymptomatic anti-HIV-positive subjects, in none of the sera obtained from asymptomatic anti-HIV-negative drug abusers, from patients with acute B and chronic C hepatitis, and from healthy donors. All positive sera reacted selectively with the GM3-comigrating band obtained from AIDS lymphocytes but not with the corresponding band from normal lymphocytes. The lymphocytic ganglioside autoantigen was revealed as GM3. In addition, two main data were shown: (a) AIDS lymphocytes have an increased concentration of GM3 and (b) the ceramide of AIDS lymphocytic GM3 has a different percentual composition of fatty acids in contrast to control cells. It is suggested that these quantitative and qualitative changes might be responsible for the appearance of circulating anti-lymphocytic GM3 antibodies.

Islet cell antibodies (ICA) bind antigens expressed in both human and rat pancreatic islets. Biochemical studies have shown that an ICA-autoantigen has the properties of a monosialo-ganglioside migrating between GM2 and GM1 standards (GM2-1). We therefore aimed to isolate and characterize gangliosides from whole pancreas and isolated islets of bio breeding diabetes-prone (BB-DP), bio breeding diabetes-resistant (BB-DR), and Wistar Furth (WF) rat strains. Gangliosides were characterized by TLC, HPLC, diode array analysis, and ganglioside-specific staining. ICA binding was studied by indirect immunostaining. The GM2-1 fraction was present in BB-DP, BB-DR, and WF rat pancreases (11, 17, and 9.5%, respectively, of total ganglioside content). Substantial differences were found in other fractions: in BB-DP pancreas, in addition to GM2-1, the main fractions were GM3 (49%), GD1a (12%), GT1b (5%), and a ganglioside migrating between GM1 and GD3 standards (23%), while in BB-DR pancreas the above components were 71, 5.5, 2, and 4.5%, respectively; in WF pancreas, the main fractions were GM3, GD3, GD1a, GT1b and a trisialoganglioside (GT*) migrating above the GT1b standard (42.7, 7, 20.2, 13.8, and 6.8, respectively). A different pattern of ganglioside expression was found in isolated islets of BB-DP, BB-DR, and WF rats: the GM2-1 fraction represented, respectively, 29.1, 30.4, and 31.6% of total ganglioside content; GM3 51.1, 66, and 68.4%. A fraction migrating between GM1 and GD3 standards was present only in BB-DP and BB-DR islets (19.8 and 3.6%, respectively). ICA-positive human sera reacted with pancreas of all rat strains studied, with similar end-point titers. In conclusion, (1) the GM2-1 ganglioside, in the same way as a putative target antigen of ICA, is equally expressed in BB-DP, BB-DR, and WF rat pancreata; and (2) the GM1-GD3 is expressed in higher amounts in BB-DP than in BB-DR pancreas and islets and is absent in WF.