Moreover, the increment of CCL2 expression in the soma of TG neurons and the infiltration of macrophages in the TG by peripheral nerve injury never occur under conditions of toll-like receptor 2 deficit, suggesting that the signaling of CCL2 released from injured neurons via toll-like receptor 2 potentiates the abundance of activated macrophage infiltration in the TG after trigeminal nerve trauma (Kim et al., 2011). The gene discussed is CCL2; the disease is peripheral nerve injury.