Changes in lipid ordering and state of aggregation in lymphocyte plasma membranes after exposure to mitogens

Abstract

An electron spin probe study was made of the effect of a number of mitogenic agents on the ordering and state of aggregation of the plasma membrane lipids of lymphocytes. These agents, which included phytohemagglutinin, Concanavalin A, the calcium ionophore A23187 and periodate, caused a 20% decrease in lipid ordering in the region of the bilayer probed by 5-nitroxide stearic acid. The corresponding methyl ester probe showed marked probe-probe interaction under the same conditions indicating an aggregation of lipids in the area probed by this label. Studies with mixed lipid vesicles and ganglioside-free cells indicate that these areas are rich in glycolipids capable of hydrogen bonding to the ester probe. The decrease in ordering and the increase in aggregation of the membrane lipids were correlated with the patching and capping of the ligand-receptor complexes. Furthermore, the disappearance of fluorescent ligand from the surface of treated cells corresponded with the return of the spectral parameters of the probes to control cell values. It was concluded that glycolipids might play an important role in ligand-induced cell surface changes either as bearers of receptor groups, as in the case of some gangliosides, or in association by hydrogen-bonding with receptor proteins.

Immunomodulatory and anti-inflammatory effects of n-3 polyunsaturated fatty acids

“…This change in fatty acid composition is accompanied by an increase in membrane fluidity (Anel et al 1990;Calder et al 1994b), although this has been a controversial subject for many years (for references, see Calder et al 1994b). In support of the proposal that membrane fluidity changes are an inherent component of lymphocyte activation and subsequent proliferation (Anel et al 1990;Calder et al 1994b), Curtain et al (1978) found that a non-mitogenic lectin (wheatgerm agglutinin) does not affect lymphocyte membrane fluidity, in contrast to the effect of the mitogenic lectins Con A and PHA. That plasma membrane fluidity does influence lymphocyte activity was shown by the studies of Maccecchini & Burger (1977) and Huber et aE.…”

Incorporation of fatty acids by concanavalin A-stimulated lymphocytes and the effect on fatty acid composition and membrane fluidity

“…Of importance, the n -6/n -3 ratio, which was approx. 10 in the control cells, was significantly increased by culture in the presence of linoleic or arachidonic acids and significantly decreased by culture in the presence of n -3 PUFA (Table 6). …”

“…The dry fihn of spin label was obtained by transferring 10 1 of a 1 mg/ml solution of 5-DOXYL-stearic acid in chloroform to a small glass tube and evaporating to dryness. The spin-labelled lymphocyte suspension was transferred to a 100,tl glass capillary tube with a sealed end.…”

“…However, these studies have yielded conflicting results, some finding no change in fluidity [8,9] and others reporting an increase [10][11][12][13][14][15][16]. Some of these studies have measured fluidity during the period immediately after activation [9][10][11][12] whereas others [8,[13][14][15][16] investigated longer-term changes.…”

Lipid composition and fluidity of the human immunodeficiency virus envelope and host cell plasma membranes.

“…Spin resonance analysis of HIV and intact, uninfected HUT-78 cells revealed that the viral envelope was approximately 11% more ordered than the lymphocyte (5). Since earlier studies of 5-NS-labeled lymphocytes indicated that this probe most likely resided in the plasma membrane and did not penetrate into intracellular membranes (47,48), we interpreted our analysis of intact cells to indicate that the spin probe was reporting the milieu of the surface membrane only. However, spectral contributions of the probe residing within intracellular membranes (i.e., a composite spectrum) could not be ruled out, since purified plasma membranes were not previously analyzed (5).…”