Apolipoprotein-mediated lipid antigen presentation in B cells provides a pathway for innate help by NKT cells

Blood. 2009 Sep 17;114(12):2411-6. doi: 10.1182/blood-2009-04-211417. Epub 2009 Jul 20.

Abstract

Natural killer T (NKT) cells are innate-like lymphocytes that recognize lipid antigens and have been shown to enhance B-cell activation and antibody production. B cells typically recruit T-cell help by presenting internalized antigens recognized by their surface antigen receptor. Here, we demonstrate a highly efficient means whereby human B cells present lipid antigens to NKT cells, capturing the antigen using apolipoprotein E (apoE) and the low-density lipoprotein receptor (LDL-R). ApoE dramatically enhances B-cell presentation of alpha-galactosylceramide (alphaGalCer), an exogenous CD1d presented antigen, inducing activation of NKT cells and the subsequent activation of B cells. B cells express the LDL-R on activation, and the activation of NKT cells by B cells is completely LDL-R dependent, as shown by blocking experiments and the complete lack of presentation when using apoE2, an isoform of apoE incapable of LDL-R binding. The dependence on apoE and the LDL-R is much more pronounced in B cells than we had previously seen in dendritic cells, which can apparently use alternate pathways of lipid antigen uptake. Thus, B cells use an apolipoprotein-mediated pathway of lipid antigen presentation, which constitutes a form of innate help for B cells by NKT cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigen Presentation / drug effects
  • Antigen Presentation / immunology*
  • Antigens, CD1d / immunology*
  • Apolipoproteins E / immunology
  • Apolipoproteins E / metabolism*
  • B-Lymphocytes / drug effects
  • B-Lymphocytes / immunology*
  • Cells, Cultured
  • Flow Cytometry
  • Galactosylceramides / pharmacology
  • Humans
  • Lymphocyte Activation / drug effects
  • Natural Killer T-Cells / drug effects
  • Natural Killer T-Cells / immunology*
  • Receptors, LDL / metabolism
  • Signal Transduction

Substances

  • Antigens, CD1d
  • Apolipoproteins E
  • Galactosylceramides
  • Receptors, LDL
  • alpha-galactosylceramide