Cyclosporine-resistant, Rab27a-independent mobilization of intracellular preformed CD40 ligand mediates antigen-specific T cell help in vitro

J Immunol. 2011 Jul 15;187(2):626-34. doi: 10.4049/jimmunol.1004083. Epub 2011 Jun 15.

Abstract

CD40L is critically important for the initiation and maintenance of adaptive immune responses. It is generally thought that CD40L expression in CD4(+) T cells is regulated transcriptionally and made from new mRNA following Ag recognition. However, recent studies with two-photon microscopy revealed that most cognate interactions between effector CD4(+) T cells and APCs are too short for de novo synthesis of CD40L. Given that effector and memory CD4(+) T cells store preformed CD40L (pCD40L) in lysosomal compartments and that pCD40L comes to the cell surface within minutes of antigenic stimulation, we and others have proposed that pCD40L might mediate T cell-dependent activation of cognate APCs during brief encounters in vivo. However, it has not been shown that this relatively small amount of pCD40L is sufficient to activate APCs, owing to the difficulty of separating the effects of pCD40L from those of de novo CD40L and other cytokines in vitro. In this study, we show that pCD40L surface mobilization is resistant to cyclosporine or FK506 treatment, while de novo CD40L and cytokine expression are completely inhibited. These drugs thus provide a tool to dissect the role of pCD40L in APC activation. We find that pCD40L mediates selective activation of cognate but not bystander APCs in vitro and that mobilization of pCD40L does not depend on Rab27a, which is required for mobilization of lytic granules. Therefore, effector CD4(+) T cells deliver pCD40L specifically to APCs on the same time scale as the lethal hit of CTLs but with distinct molecular machinery.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antigen-Presenting Cells / drug effects
  • Antigen-Presenting Cells / immunology
  • Antigen-Presenting Cells / metabolism
  • CD40 Ligand / biosynthesis
  • CD40 Ligand / physiology*
  • Cells, Cultured
  • Cyclosporine / pharmacology*
  • Cytoplasmic Granules / drug effects
  • Cytoplasmic Granules / immunology
  • Cytoplasmic Granules / metabolism
  • Drug Resistance / immunology
  • Epitopes, T-Lymphocyte / immunology*
  • Intracellular Fluid / drug effects
  • Intracellular Fluid / immunology*
  • Intracellular Fluid / metabolism*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Nude
  • Mice, Transgenic
  • T-Lymphocytes, Helper-Inducer / drug effects
  • T-Lymphocytes, Helper-Inducer / immunology*
  • T-Lymphocytes, Helper-Inducer / metabolism
  • rab GTP-Binding Proteins / physiology*
  • rab27 GTP-Binding Proteins

Substances

  • Epitopes, T-Lymphocyte
  • rab27 GTP-Binding Proteins
  • CD40 Ligand
  • Cyclosporine
  • Rab27a protein, mouse
  • rab GTP-Binding Proteins