Studies on the nature and cellular distribution of TLMA--a major rat T axis differentiation antigen. Identification as the glycosphingolipid GgOse4Cer (asialo GM1)

The Role of Glycosphingolipids in Immune Cell Functions

Glycosphingolipids (GSLs) exhibit a variety of functions in cellular differentiation and interaction. Also, they are known to play a role as receptors in pathogen invasion. A less well-explored feature is the role of GSLs in immune cell function which is the subject of this review article. Here we summarize knowledge on GSL expression patterns in different immune cells. We review the changes in GSL expression during immune cell development and differentiation, maturation, and activation. Furthermore, we review how immune cell GSLs impact membrane organization, molecular signaling, and trans-interactions in cellular cross-talk. Another aspect covered is the role of GSLs as targets of antibody-based immunity in cancer. We expect that recent advances in analytical and genome editing technologies will help in the coming years to further our knowledge on the role of GSLs as modulators of immune cell function.

Glycosphingolipids of rat T cells. Predominance of asialo-GM1 and GD1c

Glycosphingolipids play an important role in the immune response, yet their compositions in T and B cells which mediate cellular and humoral immunity, respectively, have not been elucidated. In this study, characteristic features of glycosphingolipids in rat T lineage cells were revealed by comparing the gangliosides and neutral glycolipids of spleen T- and beta-cell-enriched fractions and thymocytes. In T cells, GD1c(NeuGc,NeuGc), a unique ganglioside synthesized through asialo-GM1 (GA1), was the predominant ganglioside as previously found in thymocytes [Nohara, K., Suzuki, M., Inagaki, F., & Kaya, K. (1991) J. Biochem. (Tokyo) 110, 274-278], and the amount was much higher than in thymocytes. In addition, three other GA1-derived gangliosides were detected in T cells and identified as GM1b(NeuAc), GM1b(NeuGc), and GD1 alpha(NeuAc,NeuAc). In contrast, GD1 alpha(NeuAc,NeuAc) was not discernible in thymocytes, although gangliosides corresponding to GM1b(NeuAc) and GM1b(NeuGc) were detected. The neutral glycolipids of T cells contained almost exclusively GA1, while thymocytes contained much lower amounts. The predominance of these GA1-derived gangliosides was confirmed as a singular feature of T lineage cells by comparison with gangliosides of spleen B-cell-enriched fractions which mainly consisted of gangliosides synthesized through GM3 and GM1. Furthermore, the unique structures, which contain the GM1 core and the extended modification of the lacto series, alpha Gal-LacNAc-GM1, alpha Gal-(LacNAc)2-GM1, and sialyl-LacNAc-GM1, were found in B-cell-enriched fractions. Unexpectedly, the neutral glycolipid composition of the thymocytes resembled that of the B-cell enriched fraction rather than that of the T cells.

Trichinella pseudospiralis larvae express natural killer (NK) cell-associated asialo-GM1 antigen and stimulate pulmonary NK activity

Natural killer (NK) cell function was evaluated in mice infected with either Trichinella pseudospiralis or T. spiralis larvae. T. pseudospiralis-infected mice consistently demonstrated augmented pulmonary NK cell-mediated clearance of YAC-1 tumor cells in vivo but failed to display enhanced splenic NK cell-mediated lysis of the same tumor cells in vitro. Attempts to alter NK cell function in vivo by the injection of anti-asialo-GM1 antibody resulted in anaphylaxis and death of the hosts infected with T. pseudospiralis but not of mice infected with T. spiralis. Immunofluorescence studies demonstrated that larvae of both species bound large quantities of anti-asialo-GM1 antibody but did not react with another NK-associated antibody, anti-NK-1.1. Even though anti-asialo-GM1 antibody reacted with larvae of both species, intravenous injection of antibody elicited anaphylaxis only in hosts that were infected with T. pseudospiralis.

Comparison of the 13C-N.M.R. spectra of gangliosides GM1 with those of GM1-oligosaccharide and asialo-GM1

The 13C-n.m.r. spectra of asialo-GM1 and GM1-oligosaccharide are completely assigned and compared to those previously found for intact GM1 and for the series GM4, GM3, GM2, GM1, GD1a, GD1b, and GT1b. Removal of the ceramide residue from GM1 liberated a free, reducing aldehyde group, which was reflected in a doubling of the 13C-n.m.r. signals assignable to the D-glucose residue because of alpha, beta equilibrium. The spectrum of asialo-GM1 lacks the resonances from the sialic acid residue, as expected; in addition, several resonances from the neutral gangliotetraglycosyl residue shifted to different field positions after removal of sialic acid from GM1. These resonances include that of C-4 of the inner beta-D-galactosyl residue, and C-1 of the 2-acetamido-2-deoxy-D-galactosyl residue that is near the site of attachment of the sialosyl residue. The differences between the chemical shifts of the carbon resonances of oligomeric and monomeric saccharides, termed linkage shifts, provide a quantitative assignment aid. They are approximately 1/3 of those for residues linked to sialic acid than those for residues linked to the neutral hexose chain. Correlations among linkage shifts for pairs of glycosidically-linked carbon atoms for asialo-GM1 and GM1-oligosaccharide were compared with those for the series of gangliosides GM4 to GT1b, and differences are noted for resonances for carbon atoms near the sialic acid residue. The spectrum of ganglioside GM1b, a positional isomer of GM1 whose 13C-n.m.r. spectrum has not yet been observed, is predicted.