Plasma membrane cholesterol regulates human lymphocyte cytotoxic function

Abstract

Cell cholesterol is believed to be confined mainly to the plasma membrane. Treatment here of human peripheral blood lymphocytes with cholesterol-free and cholesterol-containing liposomes to effect, respectively, decreases or increases in cholesterol content measureable by chemical analysis, markedly altered effector functions of the cells. Depletion of cholesterol evoked inhibition of spontaneous and phytohemagglutinin-dependent lymphocyte cytotoxicity against allogeneic target cells. Opposite effects resulted from cholesterol enrichment, with PHA-dependent and antibody-dependent cytotoxicities increasing significantly. Treatment, instead, with the known inhibitor of cholesterol biosynthesis, 25-hydroxycholesterol, had suppressive effects like those resulting from lowering the cholesterol level physically by liposome treatment. Our data suggest that the plasma membrane cholesterol content of different categories of lymphocytes in man is both essential and regulatory for their cytotoxic function.

Macrophage Heterogeneity, Antigen Presentation, and Membrane Fluidity: Implications in Visceral Leishmaniasis

“…Antigen-presenting abilities of LM and SM were studied using processing independent peptide sequence, lR (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) [25] as a probe. On a comparative basis it was also observed that LM were much better antigen presenters as compared to SM.…”

“…9H 3.5 and 7B7.3 (I-A d restricted T-cell hybridoma) specific for lambda repressor N-terminal sequence 12-26 [LEDARRLKAIYEKKK, defined as lR (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)], T-cell hybridomas and peptides were kind gifts of Professor M.L. Gefter, Massachusetts Institute of Technology, Cambridge, MA, USA.…”

“…The lR(12-26) is I-A d restricted, whereas the lambda repressor sequence 80±94 [IAREIYEMYEAVSMQ, defined as lR (80±94)] is I-A k restricted [18]. Both the lR (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) and the lR(80±94) peptides show characteristics of amphipathic alpha helix and possess motif proposed by Rothbred [18].…”

“…After extensive washing when the radioactivity detected in the washing medium was less than 200 cpm, the total radioactivity of the pellet was measured. Competitive inhibition of binding of labelled peptide by unlabelled peptide was done on whole cell as described [29,30] to show the specificity of 125 IlIR (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) binding. Here the fixed Mfs were pulsed for 6 h with either unlabelled lR (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) or unlabelled unrelated peptide sequence lR(80±94) at a concentration of 5 mm and the extent of cell associated radioactivity was measured as described [31].…”

“…It was observed that 6 I-LM had no inhibitory effect on other Mf population and in fact an additive effect on antigen presentation was observed when 6 I-LM was mixed with either 6 I-SM or 6 N-SM. an unrelated sequence, lR(80±94), followed by incubation with 125 llR (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26). It was observed that pulsing with unlabelled lR(12-26) inhibited the binding of 125 llR (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) to the extent of 35% (Fig.…”