Thymic but not splenic CD8+ DCs can efficiently cross-prime T cells in the absence of licensing factors

Abstract

Cross-presentation is an important mechanism to elicit both immune defenses and tolerance. Although only a few DC subsets possess the machinery required for cross-presentation, little is known about differences in cross-presenting capabilities of DCs belonging to the same subpopulation but localized in different lymphoid organs. In this study, we demonstrate that steady-state thymic CD8+ DCs can efficiently cross-prime naïve CD8+ T cells in the absence of costimulation. Surprisingly, cross-priming by splenic CD8+ DCs was dependent on licensing factors such as GM-CSF. In the absence of GM-CSF, antigen-MHC-class-I complexes were detected on thymic but not on splenic CD8+ DCs, indicating that the cross-presentation capacity of the thymic subpopulation was higher. The observed cross-priming differences between thymic and splenic CD8+ DCs did not correlate with differential antigen capture or costimulatory molecules found on the surface of DCs. Moreover, we did not detect overall impairment of antigen presentation, as peptide-loaded splenic CD8+ DCs were able to induce CD8+ T-cell proliferation. The observation that thymic CD8+ DCs are more efficient than splenic CD8+ DCs in T-cell cross-priming in the absence of licensing factors indicates that the requirements for efficient antigen presentation differ between these cells. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.