ICAMs Are Not Obligatory for Functional Immune Synapses between Naive CD4 T Cells and Lymph Node DCs

Abstract

Protective immune responses depend on the formation of immune synapses between Tcells and antigen-presenting cells (APCs). The two main LFA-1 ligands, ICAM-1 and ICAM-2, are co-expressed on many cell types, including APCs and blood vessels. Although these molecules were suggested to be key players in immune synapses studied invitro, their contribution to helper Tcell priming invivo is unclear. Here, we used transgenic mice andintravital imaging to examine the role of dendritic cell (DC) ICAM-1 and ICAM-2 in naive CD4 Tcell priming and differentiation in skin-draining lymph nodes. Surprisingly, ICAM deficiency on endogenous CD40-stimulated lymph node DCs did not impair their ability to arrest and prime CD4 lymphocyte activation and differentiation into Th1 and Tfh effectors. Thus, functional Tcell receptor (TCR)-specific helper Tcell synapses with antigen-presenting DCs and subsequent proliferationand early differentiation into T effectors do not require LFA-1-mediated Tcell adhesiveness to DC ICAMs.