Neurite outgrowth induction by murine mesenteric lymph node explants: the effect of helminth infection.

Murine sympathetic superior cervical ganglia were co-cultured with mesenteric lymph node explants isolated from nematode Nippostrongylus brasiliensis infected mice (Nb-MLN) to examine if inflammatory cytokine response affects the ability of MLN to induce neurite outgrowth. Explants were cultured with ganglia at a distance of 1 mm in a Matrigel layer, and number of neurites towards explants were counted at 1 and 2 days in culture. While uninfected MLN exerted a smaller effect on neurite outgrowth, Nb-MLN promoted the extent of the outgrowth, and the maximum response was observed 10 days after infection. To demonstrate the roles of cytokines in the promotion of the neurite outgrowth, various anti-cytokines were added to the co-cultures. Uninfected MLN-induced neurite outgrowth was inhibited by antinerve growth factor (NGF) and anti-IL-1β. On the other hand, Nb-MLN-induced outgrowth was inhibited not only by anti-NGF and anti-IL-1β but also by anti-IL-3, anti-IL-6 and anti-GM-CSF. Since IL-1 is known to stimulate NGF production, IL -1 might be necessary for NGF-mediated neurite outgrowth in lymph nodes. Moreover, IL-3, IL-6 and GM-CSF produced during inflammation might also play important roles in the stimulation of nerve growth in vivo.