Expression of α-Fetoprotein and Interleukin 2 Receptors and Impairment of Membrane Fluidity in Peripheral Blood Mononuclear Cells from AIDS and Related Syndromes

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Abstract
We have previously shown that the expression of α-fetoprotein (AFP) receptors is impaired in mitogen-activated peripheral blood mononuclear cells (PBMCs) from HIV+ individuals and that this novel abnormality reflects an unusual proliferation response of PBMCs to mitogenic stimuli. Here we comparatively analyze, in PBMCs from patients with AIDS and related syndromes, (1) changes in membrane fluidity, measured as the cholesterol/phospholipid ratio (CH/PL), and (2) changes in the expression of AFP receptors and of the α chain of the IL-2 receptor (TAC antigen). Relative to normal cells, the expression of AFP and IL-2 receptors appeared considerably reduced in AIDS-related complex (ARC) and AIDS patients. In asymptomatic HIV+ individuals the amount of AFP receptors was within the normal range, whereas that of IL-2 receptors increased twice. CH/PL ratios were significantly lower in PHA-activated than in quiescent PBMCs from healthy donors, which implies a gain in membrane fluidity. For seropositive groups, no statistically significant changes in CH/PL ratios were appreciated on PHA activation. Nevertheless, in HIV+ asymptomatic individuals, the CH/PL ratio of quiescent PBMCs resembled that of PHA-activated PBMCs from healthy donors, suggesting that quiescent PBMCs are in a partially activated or "preactivated" status. With the worsening of the disease, toward ARC and AIDS stages, however, quiescent PBMCs from these groups showed a considerable loss in membrane fluidity, evidenced by elevated values of the CH/PL ratio. This radical change strongly suggest a severe alteration of the lipid metabolism in these cells. Thus, HIV infection impairs the fluidity of the cell membrane and, because the latter influences a large number of cellular functions, it may contribute to the progress of the disease by altering normal sequences of lymphocyte activation and blastic transformation.