ABSTRACT
UVB radiation has been shown to induce T cell tolerance most likely via modulation of the function of antigen-presenting cells like dendritic cells (DC), which are therefore of interest for vaccination therapy. Since little is known about the effects of UVB-irradiated dendritic cells (UVB-DC) on CD8(+) T cells, which are the dominant effectors in various allergic and autoimmune diseases, we have investigated the potential of low dose UVB (100-200 J per m(2)) irradiated bone marrow-derived dendritic cells to induce tolerance in murine CD8(+) T cells specific for the contact allergen trinitrophenyl (TNP) or for a viral peptide. In contrast to the previously reported successful tolerization of primed CD4(+) Th1 cells, neither naïve CD8(+) T cells nor CD8(+) Tc1 effector cells or established CD8(+) T cell clones could be tolerized by TNP-modified or peptide-pulsed UVB-DC in vitro or in vivo. We observed, however, a reduced capacity of UVB-DC to prime naïve CD8(+) T cells. Our data demonstrate an important difference in the susceptibility of CD4(+) and CD8(+) T cells for tolerance induction using low-dose UVB-irradiated DC and have implications for DC therapy of CD8(+) T cell-mediated diseases.
Subject(s)
CD8-Positive T-Lymphocytes/immunology , Dendritic Cells/immunology , Dendritic Cells/radiation effects , Immune Tolerance , T-Lymphocytes, Regulatory/immunology , Ultraviolet Rays , Adoptive Transfer , Animals , Cells, Cultured , Dermatitis, Allergic Contact/etiology , Dermatitis, Allergic Contact/immunology , Epitopes , Ligands , Mice , Mice, Inbred C57BL , Receptors, Antigen, T-Cell/metabolism , TrinitrobenzenesABSTRACT
Low dose UVB irradiation of dendritic cells (DC) dose-dependently decreases their allostimulatory capacity and inhibits alloreactive T cell proliferation. The reduction of the stimulatory capacity is not associated with a perturbation of CD28 costimulation. To examine the underlying mechanism, cell cycle analysis of T cells from cocultures with UVB-irradiated DC (UVB-DC) was performed, revealing no cell cycle arrest, but an increased number of apoptotic T cells in sub-G(0) phase. We confirmed T cells to undergo apoptosis after coincubation with UVB-DC by TUNEL staining and DNA laddering. To analyze whether T cell apoptosis requires the Fas/Fas ligand (FasL) pathway, MLRs were performed with Fas-, FasL-deficient, and wild-type DC and T cells. No differences were found on comparison of wild-type DC with Fas-/FasL-deficient DC or T cells. Likewise, addition of a neutralizing anti-TNF-alpha mAb to cocultures could not overcome inhibition of T cell proliferation by UVB-DC, excluding involvement of the TNF-alpha/TNF-alphaR pathway. FACS analysis of CD69 and CD25 revealed no up-regulation on T cells cocultured with UVB-DC, suggesting a perturbation of early T cell activation. Analysis of UVB-DC by confocal microscopy demonstrated impaired filamentous actin bundling, a process critical for T cell stimulation. To investigate the functional relevance of these observations, time lapse video microscopy was performed. Indeed, calcium signaling in CD4(+) T cells was significantly diminished after interaction with UVB-DC. In conclusion, UVBR of DC impairs their cytoskeletal rearrangement and induces apoptosis in CD4(+) T cells by disruption of early DC-T cell interaction, resulting in a reduced Ca(2+) influx in T cells.
