A subset of cytolytic dendritic cells in rat

Dendritic cells (DCs) are a rare population of leukocytes specialized in Ag processing and presentation to T cells, We have previously shown that cult ured rat splenic:DCs exhibit a cytotoxic activity against selected target c ells. 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 stro ng and moderate cytotoxic activity against YAC-1 and K562 target cells, res pectively, FAGS analyses showed that spleen contained a minor subset (10-15 %) of CD4(+) and class IIint DCs that also expressed the OX41 Ag and the ly mphoid-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 DC s 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+-independ ent mechanism, but this function did not appear mediated by Pas ligand, TNF -related apoptosis-inducing ligand, or TNF-alpha. Therefore, rat DCs contai n a subset of naturally cytolytic cells that could play a role in both inna te 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.