MHC class I-restricted killing of neurons by virus-specific CD8+ T lymphocytes is effected through the Fas/FasL, but not the perforin pathway,.
Induction of MHC class I genes in neurons of the central nervous system requires signals by pro-inflammatory cytokines, in particular IFN-gamma, and the blockade of electric activity, which is known to suppress induction of MHC related genes in a highly ordered, but unusual fashion [1], [2]. The present experiments explore the immunological function of neuronal MHC class I antigens expressed under permissive conditions. MHC class I proteins were induced in electrically silenced murine hippocampal neurons by treatment with the sodium channel blocker tetrodotoxin and recombinant IFN-gamma, conditions which also resulted in the induction of Fas molecules. The MHC class I positive neurons were challenged with CD8+ cytotoxic T lymphocytes (CTL) specific for the H2-Db binding peptide GP33, a dominant epitope of the lymphocytic choriomeningitis virus envelope glycoprotein, or with alloreactive CTL. Single primed neurons, attacked by GP33-specific CTL, were continuously monitored for changes in intracellular calcium ([Ca2+]i), an indicator of cytotoxic damage. MHC class I-induced neurons pulsed with the GP33 peptide, but not a control peptide, showed a gradual and sustained increase in [Ca2+]i within 3 h following attack by GP33-specific CTL, while in astrocytes [Ca2+]i elevation was rapid. The slow course of the neuronal response was consistent with a delayed apoptotic killing mechanism rather than rapid granule-mediated plasma membrane lysis. Indeed, the attacked neurons bound annexin V, indicating membrane alterations preceding apoptotic cell death. In further support of apoptotic cell death, this sustained increase of [Ca2+]i levels was also observed following attack by perforin-deficient CTL, but was not detected in neurons derived from mutant lpr mice, which lack functional Fas molecules.
Medana
I M
IM
Department of Neuroimmunology, Max-Planck Institute of Neurobiology, Martinsried, Germany.
Gallimore
A
A
Oxenius
A
A
Martinic
M M
MM
Wekerle
H
H
Neumann
H
H
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D053222:Fas Ligand Protein; D015395:Histocompatibility Antigens Class I / Q000502:physiology*; D008217:Lymphocytic choriomeningitis virus / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000473:pathology*; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D051381:Rats; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014764:Viral Proteins / Q000276:immunology*; D019014:fas Receptor / Q000502:physiology*
D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; C505662:Faslg protein, rat; D015395:Histocompatibility Antigens Class I; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D014764:Viral Proteins; D019014:fas Receptor; D054353:Perforin; D002118:Calcium