Human monocyte/macrophages activate by exposure to LPS overexpress NGF and NGF receptors.

Monocyte/macrophages (M/M) represent the main cellular component of the immune system involved in the inflammatory response. In the present study we investigate whether NGF is produced by M/M and is involved in this event. The results show that unstimulated human M/M produce NGF and its synthesis is stimulated by LPS. The increase of NGF is associated with enhanced expression of high affinity NGF receptor on M/M and with no changes of low affinity NGF receptors (p75). The neutralization of endogenous NGF by NGF antibody in LPS-activated M/M, leads to overexpression of p75 receptor causing apoptosis. These findings provide new insight in the mechanisms governing monocyte survival in the inflamed tissue, representing a crucial aspect of host defence and maintenance of homeostasis.