The major gangliosides of human peripheral blood monocytes/macrophages: absence of ganglio series structures

Sialoglycosphingolipids (gangliosides) are membrane components of eukaryoti c cells that modulate cell signal transduction events. Discrepancies exist in the published descriptions of the gangliosides present in the human peri pheral monocyte/macrophage. Macrophages were isolated from healthy human vo lunteers by two different methods. Their ganglioside fractions were isolate d and examined by 2D thin-layer mobility, enzymatic susceptibility, and mas s spectral-collision induced dissociation-mass spectral analyses. Thin-laye r ganglioside chromatographic patterns displayed four major doublets and we re similar for monocytes/macrophages isolated by either apheresis/elutriati on or density gradient centrifugation. An gangliosides were resistant to P- galactosidase but sensitive to Clostridium perfringens sialidase, indicatin g the absence of terminal galactose residues and sialidase-resistant sialic acid moieties. Mass spectra indicated only three major sets of glycolipid components with mass heterogeneity in the ceramide portion of each set. In an the gangliosides, the ceramide moiety contained only C18 sphingosine wit h the heterogeneity produced by the presence of C16 or C24 fatty acid. One doublet was resistant to Newcastle disease virus sialidase, indicating the presence of an alpha (2-6)-linked sialic acid residue with the same mass as another doublet. All data was consistent with the following structures as the major gangliosides of human peripheral monocyte/macrophages: II(3)NeuAc LacCer (sialolactosyl ceramide, GM3), IV3- and IV(6)NeuAcnLcOSe(4)Cer (sial oparagloboside, nLM1), and IV(3)NeuAcnLcOse(6)Cer,Cer (a sialohexosylcerami de).