A Subset of Cytolytic Dendritic Cells in Rat

Abstract

Dendritic cells (DCs) are a rare population of leukocytes specialized in Ag processing and presentation to T cells. We have previously shown that cultured rat splenic DCs exhibit a cytotoxic activity against selected target cells. In this study, we analyzed this function in DCs freshly prepared from lymphoid organs using the DC-specific OX62 mAb and magnetic beads. Freshly extracted splenic DCs, but not lymph node and thymic DCs, exhibited a strong and moderate cytotoxic activity against YAC-1 and K562 target cells, respectively. FACS analyses showed that spleen contained a minor subset (10–15%) of CD4+ and class IIint DCs that also expressed the OX41 Ag and the lymphoid-related Ags CD5 and CD90 (Thy-1) and a major (80–85%) subset of CD4−/OX41−/CD5− and class IIint DCs. The cytotoxic activity of splenic DCs was strictly restricted to the CD4− DCs, a subset poorly represented in LN and thymus. Contrasting with our previous report using cultured splenic DCs, freshly isolated splenic DCs killed YAC-1 cells using a Ca2+-independent mechanism, but this function did not appear mediated by Fas ligand, TNF-related apoptosis-inducing ligand, or TNF-α. Therefore, rat DCs contain a subset of naturally cytolytic cells that could play a role in both innate and acquired immune responses. Together with our previous report, these data suggest that rat DCs can use two mechanisms of cytotoxicity depending on their maturation/activation state.