Cross-linking of cell surface ganglioside GM1 induces the selective apoptosis of mature CD⁺ T lymphocytes

Abstract

Gangliosides are glycosphingolipids found ubiquitously on the surface of mammalian cells. They contain a ceramide tail that is inserted into the membrane and exposed carbohydrate and sialic acid moieties. The non-toxic B subunit oligomer (EtxB) of Escherichia coli heat-labile enterotoxin (Etx) is a potent immunogen in vivo and has profound modulatory effects on EtxB-primed lymphocytes in vitro, properties which are dependent on its ability to bind to GM1 ganglioside receptors. Here, it is shown that cross-linking GM1 by EtxB causes a differential effect on mature CD4(+) and CD8(+) T cells from lymph node cultures proliferating in response to an unrelated antigen, ovalbumin. Addition of EtxB to such cultures led to the complete depletion of CD8(+) T cells compared with enhanced activation of CD4(+) cells [as measured by expression of CD25 (IL-2Ralpha)]. By contrast, addition of a mutant EtxB, EtxB(G33D), which does not bind to GM1, failed to trigger CD8(+) T cell depletion. When EtxB was added to isolated non-immune CD8(+) lymphocytes rapid (12-18 h) alterations in nuclear morphology and the appearance of sub-G0/G1 levels of DNA were induced; properties which are characteristic of cells undergoing apoptosis. EtxB(G33D) failed to trigger apoptosis, indicating that the induction of the apoptotic signal was dependent on the binding of GM1. These findings provide an insight into the potent immunogenicity and immunomodulatory properties of E. coli enterotoxins as well as heralding a novel method for the selective induction of apoptosis in mature CD8(+) T lymphocytes.

CD4 and CD8 T cells require different membrane gangliosides for activation

“…The presence in a single cell of a variety of rafts with different gangliosides has been suggested (4,5). Cross-linking gangliosides using CTx-B or a homolog, the heat-labile enterotoxin of Escherichia coli, can induce apoptosis in CD8 + T cells but not in CD4 + T cells (20), which results from the induction of caspase-dependent signaling caused by activation of NF-κB and c-Myc (20). Although this process is known to proceed in a Fas-and p55 tumor necrosis factor receptor-independent pathway (21), the events in rafts following the ganglioside cross-linking remain undetermined.…”

Apoptosis Induced In Vitro and In Vivo During Infection by Ebola and Marburg Viruses

“…The increased number of CD4 ϩ T cells and apoptotic cells seen in germinal centers of filovirus-infected monkeys suggests that Fas ligand interaction may not only be important for the observed plasma cell apoptosis, but may also be involved in germinal center disruption. Finally, a report demonstrating selective depletion of CD8 ϩ T cells by cross-linking of the cell surface ganglioside GM1 (Nahar et al, 1996) raises the possibility of selective apoptosis of individual cell phenotypes through this or similar mechanisms.…”

“…The increased number of CD4 ϩ T cells and apoptotic cells seen in germinal centers of filovirus-infected monkeys suggests that Fas ligand interaction may not only be important for the observed plasma cell apoptosis, but may also be involved in germinal center disruption. Finally, a report demonstrating selective depletion of CD8 ϩ T cells by cross-linking of the cell surface ganglioside GM1 (Nahar et al, 1996) raises the possibility of selective apoptosis of individual cell phenotypes through this or similar mechanisms.It is intriguing that, while apoptotic lymphocytes were commonly seen in filovirus-infected tissues and cultures of human PBMC, apoptosis was not seen in filovirus-infected cells. These observations raise questions regarding the causes and implications of a productive infection that does not induce apoptosis.…”

The Pathway of Antigen Uptake and Processing Dictates MHC Class II-Mediated B Cell Survival and Activation

“…We therefore examined whether ligation of CII-peptide leading to the loss of B cells observed above is associated with DNA fragmentation, a hallmark of cells undergoing the classical type of apoptosis. For this purpose, we used our established method for cell cycle analysis of primary cells to detect DNA fragmentation (14). Purified B cells from the spleen of nontransgenic mice were incubated overnight with 100 M HEL with and without C4H3 mAb.…”