ABSTRACT
The role of A. laidlawii membrane lipids in the organism's interaction with mouse spleen lymphocytes is analyzed. A. laidlawii cells were grown in a lipid-poor medium with unsaturated fatty acids that allowed cells with different degrees of membrane lipid microviscosity to be obtained. The intensity of the binding of A. laidlawii cells and derived liposomes with lymphocytes depended directly on the degree of fatty acid unsaturation. Cholesterol incorporation into the A. laidlawii membrane reduced the fluidity of the lipid bilayer and decrease the binding activity. The intensity of cholesterol transfer from lymphocytes to A. laidlawii also depended on the degree of fatty acid unsaturation in A. laidlawii cells. Cells enriched with cholesterol took up considerably less of this sterol from lymphocytes. The loss of cholesterol as well as the enrichment of lymphocytes by A. laidlawii membrane fatty acids resulted in a decrease in the microviscosity of lymphocyte membrane lipids. It was concluded that the ability of A. laidlawii cells or derived liposomes to stimulate the transport of carbohydrates into lymphocytes depended on the degree of unsaturation of fatty acid incorporated into A. laidlawii. Cholesterol also decreased the stimulatory effect, probably by lowering carbohydrate carrier mobility.
Subject(s)
Acholeplasma laidlawii/metabolism , Lymphocytes/microbiology , Membrane Lipids/physiology , Animals , Carbohydrate Metabolism , Cell Membrane/metabolism , Cholesterol/physiology , Culture Media , Fatty Acids, Unsaturated/physiology , Liposomes/metabolism , Mice , Temperature , ViscosityABSTRACT
Transport of two non-metabolized carbohydrates (3-O-methyl-D-glucose, 3-O-MG, and 2-deoxy-D-glucose, 2-DG) into mouse spleen lymphocytes after their interaction with Acholeplasma laidlawii cells has been studied. Incubation of A. laidlawii cells and particularly the liposomes prepared from A. laidlawii membrane lipids enhances the rates of the both carbohydrates transport. This treatment resulted in increasing of the Vmax values of 3-O-MG and 2-DG without changing the Km values. This stimulation can be explained by the increasing of the mobility of membrane carbohydrates carriers as a result of the exchange of lipid components between Acholeplasma and lymphocyte membranes. Actually, it has been shown that liposomes derived from A. laidlawii cells grown on the medium with great amount of unsaturated oleic acid stimulate the transport activity more actively than liposomes prepared from the cells grown on the medium with bovine serum or with oleic acid plus cholesterol. It should be suggested that an activation of carbohydrates transport into lymphocytes caused by alteration of the carriers lipid microenvironment.
Subject(s)
Acholeplasma laidlawii/physiology , Deoxy Sugars/metabolism , Deoxyglucose/metabolism , Lymphocytes/metabolism , Membrane Fluidity , Methylglucosides/metabolism , Methylglycosides/metabolism , 3-O-Methylglucose , Animals , Biological Transport , Liposomes , Lymphocytes/microbiology , Membrane Lipids/metabolism , Mice , Spleen/cytologyABSTRACT
The duration of Acholeplasma laidlawii antigen persistence in mice, resistant to Rausher leukemia virus, after infection with both A. laidlawii cells and Rausher virus has been studied. The antigen persistence was accompanied by marked depression of immune response which was especially severe in case of mixed acholeplasmavirus infection. Such immunosuppression and observed infiltration of the spleen with immature leukemic cells can be regarded as a preleukosis. Immunosuppression was accompanied by an increase of the transport of carbohydrates inthe lymphocytes. This stimulation an be explained by the exchange of lipid components between acholeplasma and lymphocyte membranes resulted in increase of lymphocyte membrane fluidity, or it may be due to the mitogenic effect of A. laidlawii cells and virus, accompanied by the same membrane effect.
Subject(s)
Acholeplasma laidlawii/immunology , Leukemia, Experimental/immunology , Lymphocytes/immunology , Mycoplasmatales Infections/immunology , 3-O-Methylglucose , Animals , Antigens, Bacterial/immunology , Deoxyglucose/metabolism , Female , Fluorescent Antibody Technique , Leukemia, Experimental/complications , Lymphocytes/metabolism , Male , Methylglucosides/metabolism , Mice , Mycoplasmatales Infections/complications , Rauscher Virus/immunology , Rosette Formation , Spleen/cytology , Spleen/immunologyABSTRACT
Interaction between Acholeplasma laidlawii cells labelled with oleic acid and mouse spleen lymphocytes depended on the time of incubation, on the temperature and on the quantitative ratio between both cells. Uncouplers and EDTA did not influence the intensity of attachment. The resistance of binding to cytochalasin B amd glutaraldehyde as well as localization of A. laidlawii antigens on the lymphocyte surface and experiments with [14C] uridine-labelled mycoplasmas are an evidence against the participation of pinocytosis in this interaction. Prolonged attachment of intact A. laidlawii to washed lymphocytes can be excluded on the basis of an extremely low amount of CFU recovered from disrupted lymphocytes as well as by experiments with uridine-labelled A laidlawii. Specific receptors didn't take part in the binding, because proteolytic enzymes and neuraminidase treatment proved to be nonefficient. Increased binding of lymphocytes with liposomes prepared from mycoplasma lipids as well as the transfer of cholesterol from lymphocyte membrane to mycoplasma membrane demonstrate the participation of membrane lipids in this binding. It should also be mentioned that after the attachment between both cell types and fusion of A. laidlawii cells with lymphocytes takes place. The transfer of unsaturated fatty acids from mycoplasmas into lymphocyte membrane as well as lymphocyte membrane cholesterol into mycoplasma membranes are the consequence of fusion between both cells. The experiments with uncharged hydrophobic fluorescent probe 4-DMC are the direct proof of fusion and mutual exchange of lipid membrane components.
