MRL/lpr CD4- CD8- and CD8+ T cells, respectively, mediate Fas-dependent and perforin cytotoxic pathways

Eur J Immunol. 1997 Feb;27(2):415-20. doi: 10.1002/eji.1830270211.

Abstract

Autoimmune-prone MRL/lpr mice, homozygous for the lpr mutation, exhibit defective apoptosis and develop generalized lymphoproliferation with the accumulation of a double-negative (DN: CD4- CD8-) T cell population. The capacity of lpr T lymphocytes to effectuate Fas- and perforin-mediated cytotoxicity was investigated. Spleen and lymph nodes cells spontaneously lyse Fas- targets (thymocytes) through a Fas-mediated mechanism as a consequence of their overexpression of Fas ligand (FasL) confirmed by semiquantitative reverse transcription (RT)-PCR and immunoprecipitation analysis. This cytotoxicity was greatly increased after stimulation of the effectors by phorbol myristate acetate (PMA) + ionomycin. Under these conditions, MRL/lpr spleen and LN cells exhibited strong Fas-mediated Ca2+-independent cytotoxic activity against wild-type Fas+ (H-2 compatible or incompatible) thymocytes or lipopolysaccharide (LPS)-transformed blast cells. Such Fas-mediated cytotoxic activity was also observed with C57BL/6-lpr, but never with wild-type C57BL/6 or MLR+/+ effectors. Depletion experiments showed that the effector cells of this Fas-mediated cytotoxicity were DN T cells. This subset, which represent in vivo activated T cells, can spontaneously lyse Fas+ targets by a mechanism that does not need the interaction of the T cell receptor (TCR) with major histocompatibility complex molecule plus antigen. This lytic potential is increased by PMA + ionomycin, which sends a second activation signal to these primed T cells. Therefore, the small amounts of Fas receptor expressed on MRL/lpr tissues may account for their nonspecific autoimmune attack by DN cells. In Con A-containing medium, which allows detection of the perforin-mediated pathway against Fas targets, cytotoxic CD8+ effectors were detected that are able to kill lpr thymocytes via a Ca2+-dependent pathway. Thus, in MRL/lpr mice, these CD8+ cells could constitute potent cytotoxic effectors against cells presenting antigen to their TCR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CD4 Antigens / analysis*
  • CD8 Antigens / analysis*
  • Cells, Cultured
  • Concanavalin A / analysis
  • Culture Media / chemistry
  • Cytotoxicity, Immunologic / immunology*
  • Fas Ligand Protein
  • Ionomycin / analysis
  • Ligands
  • Membrane Glycoproteins / biosynthesis
  • Membrane Glycoproteins / immunology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred DBA
  • Mice, Inbred MRL lpr
  • Perforin
  • Pore Forming Cytotoxic Proteins
  • T-Lymphocyte Subsets / immunology*
  • T-Lymphocytes, Cytotoxic / immunology*
  • T-Lymphocytes, Cytotoxic / metabolism
  • Tetradecanoylphorbol Acetate / analysis
  • fas Receptor / immunology*

Substances

  • CD4 Antigens
  • CD8 Antigens
  • Culture Media
  • Fas Ligand Protein
  • Fasl protein, mouse
  • Ligands
  • Membrane Glycoproteins
  • Pore Forming Cytotoxic Proteins
  • fas Receptor
  • Concanavalin A
  • Perforin
  • Ionomycin
  • Tetradecanoylphorbol Acetate