The initiation of a primary immune response requires contact
between dendritic cells (DCs) and resting T cells. However, little is known
about the proteins that mediate this initial contact. We show here that
neuropilin-1, a receptor involved in axon guidance, was expressed by human DCs
and resting T cells both in vitro and in vivo. The initial
contact between DCs and resting T cells led to neuropilin-1 polarization on T
cells. DCs and resting T cells specifically bound soluble neuropilin-1, and
resting T cells formed clusters with neuropilin-1−transfected COS-7 cells
in a neuropilin-1−dependent manner. Functionally, preincubation of DCs or
resting T cells with blocking neuropilin-1 antibodies inhibited DC-induced
proliferation of resting T cells. These data suggest that neuropilin-1 mediates
interactions between DCs and T cells that are essential for initiation of the
primary immune response and show parallels between the nervous and immune
systems.
