Dendritic cell ICAM-1 strengthens synapses with CD8 T cells but is not required for their early differentiation

Abstract

Lymphocyte priming in lymph nodes (LNs) was postulated to depend on the formation of stable Tcell receptor (TCR)-specific immune synapses (ISs) with antigen (Ag)-presenting dendritic cells (DCs). The high-affinity LFA-1 ligand ICAM-1 was implicated in different ISs studied invitro. We dissect the invivo roles of endogenous DC ICAM-1 in Ag-stimulated Tcell proliferation and differentiation and find that under type 1 polarizing conditions in vaccinated or vaccinia virus-infected skin-draining LNs, Ag-presenting DCs engage in ICAM-1-dependent stable conjugates with a subset of Ag-specific CD8 blasts. Nevertheless, in the absence of these conjugates, CD8 lymphocyte proliferation and differentiation into functional cytotoxic Tcells (CTLs) and skin homing effector lymphocytes takes place normally. Our results suggest that although CD8 Tcell blasts engage in tight ICAM-1-dependent DC-T ISs, firm ISs are dispensable for TCR-triggered proliferation and differentiation into productive effector lymphocytes.