Phenotypic and Functional Characterization of Mouse Hepatic CD8α+ Lymphoid-Related Dendritic Cells

Recently, attention has focussed on phenotypic and functional differences between classic myeloid dendritic cells (DC), and DC that reportedly develop from an early, committed lymphoid precursor. In mice, DC from these separate hemopoietic lineages differ by their surface expression of CD8 alpha. We undertook a comparative study of CD8 alpha+ (CD11blow; lymphoid-related) and CD8 alpha- (CD11bhigh; myeloid) DC isolated from mouse liver. CD8 alpha+ and CD8 alpha- DC each constituted </=1.0% of the freshly isolated, normal nonparenchymal cells (NPC). Both populations were enriched 10-15% by overnight culture and metrizamide density centrifugation. Flt3 ligand (Flt3L) potently induced equal expansion of both subsets in vivo. Tissue-resident CD8 alpha+ DC, freshly isolated from Flt3L-treated mice, existed primarily as immature cells (CD11c+, CD11blow, CD40-/low, CD80low, CD86low, MHC class IIlow), consistent with previous observations regarding bulk DC freshly isolated from nonlymphoid tissues. Following overnight culture in GM-CSF, CD8 alpha+ DC underwent phenotypic and functional maturation equivalent to that observed for CD8 alpha- DC. CD95 ligand (FasL) mRNA was detected in both immature and mature DC of each subset. In vitro analysis confirmed that flow-sorted, mature CD8 alpha+ and CD8 alpha- DC were strong and equally efficient stimulators of allogeneic T cell proliferation in primary MLR. Both immunohistochemical and genomic DNA analysis revealed that in vivo, sorted CD8 alpha+ DC trafficked from s.c. sites to T cell areas of allogeneic lymphoid tissue and were equally efficient at priming naive T cells compared with CD8 alpha- DC. This is the first comparative study of lymphoid-related DC isolated from nonlymphoid tissue.