Modification of membrane cholesterol level affects expression and clustering of class I HLA molecules at the surface of JY human lymphoblasts

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Abstract

Recently we have found that class I HLA molecules, key elements of the antigen presentation system for CD8+ effector cells, show a clustered lateral distribution (homoassociation) at the surface of activated human T- and B-lymphocytes as well as virus-transformed T- and B-lymphoblasts, in contrast to a disperse distribution on resting human PBLs (Matko et al. (1994) J. Immunol. 152, 3353; Bene et al. (1994) Eur. J. Immunol. 24, 2115). Expression of β2m-free HLA heavy chains and exogenous β2m have been shown as potential regulation factors of HLA-I clustering, which in turn may affect cytotoxic activity of CD8+ effector cells. Here we report a study on the effect of plasma membrane-modification (by exogenous cholesterol and phosphatidylcholine) on the expression of free HLA heavy chains and β2m-bound HLA-I molecules on JY human B-lymphoblasts. The modulating effect of these two treatments on the lipid fluidity of cells was demonstrated by fluorescence anisotropy of DPH lipid probe. The lateral clustering (association) of HLA-I molecules was detected by flow cytometric fluorescence resonance energy transfer (FCET) and digital imaging microscopic photobleaching energy transfer (pbFRET) methods, using flourescein-isothiocyanate (FITC) (donor)- and tetramethyl-rhodamine-isothiocyanate (TRITC) (acceptor)-labeled W6/32 or KE2 antibodies directed against intact HLA-I molecules. Cholesterol enrichment of the plasma membrane increased membrane fluidity and reduced the expression of heavy- and light-chain determinants of HLA-I molecules and free heavy chains (FHCs). This was accompanied with a higher degree of HLA-I clustering as shown by the enhanced intermolecular energy transfer efficiency. In contrast, cholesterol depletion resulted in membrane fluidization and increased expression of HLA-I epitopes. Our results suggest that both cholesterol level and lipid structure/fluidity of the plasma membrane in lymphoblastoid cells may also potentially regulate lateral organization and consequently the presentation efficiency of HLA-I molecules.

Original languageEnglish
Pages (from-to)221-226
Number of pages6
JournalImmunology letters
Volume54
Issue number2-3
DOIs
Publication statusPublished - Dec 2 1996

Keywords

  • HLA
  • cholesterol
  • clustering
  • free class I heavy chains
  • membrane fluidity

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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