g(m1)-ganglioside and Leukemia--T-Cell

Subunits (alpha, beta and gamma) of the interleukin-2 receptor complex (IL-2R) are involved in both proliferative and activation-induced cell death (AICD) signaling of T cells. In addition, the signaling beta and gamma chains are shared by other cytokines (e.g. IL-7, IL-9, IL-15). However, the molecular mechanisms responsible for recruiting/sorting the alpha chains to the signaling chains at the cell surface are not clear. Here we show, in four cell lines of human adult T cell lymphoma/leukemia origin, that the three IL-2R subunits are compartmented together with HLA glycoproteins and CD48 molecules in the plasma membrane, by means of fluorescence resonance energy transfer (FRET), confocal microscopy and immuno-biochemical techniques. In addition to the beta and gamma(c) chains constitutively expressed in detergent-resistant membrane fractions (DRMs) of T cells, IL-2Ralpha (CD25) was also found in DRMs, independently of its ligand-occupation. Association of CD25 with rafts was also confirmed by its colocalization with GM-1 ganglioside. Depletion of membrane cholesterol using methyl-beta-cyclodextrin substantially reduced co-clustering of CD25 with CD48 and HLA-DR, as well as the IL-2 stimulated tyrosine-phosphorylation of STATs (signal transducer and activator of transcription). These data indicate a GPI-microdomain (raft)-assisted recruitment of CD25 to the vicinity of the signaling beta and gamma(c) chains. Rafts may promote rapid formation of a high affinity IL-2R complex, even at low levels of IL-2 stimulus, and may also form a platform for the regulation of IL-2 induced signals by GPI-proteins (e.g. CD48). Based on these data, the integrity of these GPI-microdomains seems critical in signal transduction through the IL-2R complex.

Topics: Antigens, CD; CD48 Antigen; G(M1) Ganglioside; Glycoproteins; HLA Antigens; Humans; Interleukin-2 Receptor alpha Subunit; Leukemia, T-Cell; Lymphoma, T-Cell; Membrane Microdomains; Receptors, Interleukin; Receptors, Interleukin-2; Signal Transduction; Tumor Cells, Cultured

To develop an experimental model of adult T-cell leukemia/lymphoma in small animals, severe combined immunodeficiency (SCID) mice treated with anti-asialo GM-1 antibody were inoculated with MT-2 cells, a cell line transformed by the human T-cell leukemia virus (HTLV-I). Three mice injected with 4 x 10(7) cells subcutaneously or intramuscularly developed tumors at or near inoculation sites. Immunofluorescent antibody (IFA) staining for HTLV-I structural protein, p19, revealed the specific antigen in the cytoplasm of most cells from tumors and the DNA signals of HTLV-I proviral DNA were also positive in cellular DNA by polymerase chain reaction assay with HTLV-I tax gene primers, SK43/SK44. The MT-2 cells did not invade in mouse organs.

Topics: Animals; Antibodies; Cell Line, Transformed; Cell Transformation, Viral; DNA, Neoplasm; Fluorescent Antibody Technique; G(M1) Ganglioside; Human T-lymphotropic virus 1; Humans; Leukemia, T-Cell; Lymphoma, T-Cell; Mice; Mice, SCID; Neoplasm Transplantation; Polymerase Chain Reaction; T-Lymphocytes; Transplantation, Heterologous

We have explored the possible mechanisms for selective modulation by gangliosides of CD4 on human T lymphocytes and subsequent re-expression of CD4. Indirect immunofluorescence staining with anti-CD4 antibodies revealed newly internalized CD4 in ganglioside-treated cells after membrane permeabilization with 0.1% saponin. Cycloheximide and other metabolic inhibitors did not alter the modulation but inhibited significantly the re-expression of CD4. These results suggest both selective modulation of CD4 by a process of endocytosis and re-expression of CD4 through de novo protein synthesis.

Topics: Antigens, Differentiation, T-Lymphocyte; Blotting, Western; Cell Membrane; Cell Membrane Permeability; Cholera Toxin; Dose-Response Relationship, Drug; Fluorescein-5-isothiocyanate; Fluoresceins; Fluorescent Antibody Technique; Fluorescent Dyes; G(M1) Ganglioside; Gangliosides; Humans; Leukemia, T-Cell; Saponins; T-Lymphocytes; Thiocyanates; Tumor Cells, Cultured

As the first step in human immunodeficiency virus (HIV) infection, HIV binds to CD4 molecules on the surface of human T lymphocytes. Expression of CD4 by the cells is remarkably modulated by exogenously added gangliosides, which are normal components of the surface of animal cells. We report here that these physiological molecules also clearly inhibited HIV infection of lymphocytes in vitro in a dose-dependent manner through the selective modulation of CD4 from the cell surface. This raises the possibility of in vivo application of gangliosides as a new strategy for treating acquired immunodeficiency syndrome.

Topics: Antibodies, Monoclonal; CD4 Antigens; Cell Line; G(M1) Ganglioside; HIV; Humans; Leukemia, T-Cell; T-Lymphocytes; Tumor Cells, Cultured

Anti-reovirus cytotoxic effectors were found to be: (i) H-2 restricted; (ii) virus specific; (iii) non-lytic (in 4 h) for natural killer (NK)-sensitive YAC-1 cells; and (iv) positive for the Thy-1 and Lyt-2 lymphocyte markers. Thus, anti-reovirus cytotoxic effectors have the functional and phenotype characteristics of cytotoxic T lymphocyte (CTL). A significant fraction of anti-viral CTL, as well as alloreactive CTL, were also found to be positive for the asialo GM1 (ASGM1) cell surface antigen, generally considered to be a NK cell marker. ASGM1 expression on these CTL, as determined by sensitivity to antibody plus complement (C), appeared to be highly variable and dependent on two factors-the nature of the antigenic stimulus (viral vs. alloantigen), and the mouse strain from which the CTL originated. Thus, ASGM1 antigen expression on CTL appears to be regulated and may be under the control of lymphokines, development differentiation signals and/or other strain-dependent genetic factors.

Topics: Animals; Antigens, Surface; Fibroblasts; G(M1) Ganglioside; Genetic Variation; Glycosphingolipids; H-2 Antigens; Isoantibodies; Killer Cells, Natural; Leukemia, T-Cell; Lymphocyte Depletion; Mice; Mice, Inbred Strains; Reoviridae; T-Lymphocytes, Cytotoxic; Thy-1 Antigens; Tumor Cells, Cultured