Altered plasma nerve growth factor-like immunoreactivity and nerve growth factor-receptor expression in human old age

BACKGROUND: Nerve growth factor (NGF), discovered because of its action on cells in the peripheral and the central nervous system, is now known to act also on immune cells in developing and adult subjects. Whether peripheral lymphocytes of aged subjects are responsive to this molecule is less clear. OBJECTIVE: Aim of our study was to investigate whether or not plasma NGF undergoes any significant changes during aging and whether or not NGF receptors on peripheral lymphocytes are affected in old subjects. METHODS: To address these questions, we used RT-PCR, immunohistochemistry, and immunoenzymatic analysis to evaluate the expression of NGF receptors in human peripheral lymphocytes and NGF-like immunoreactivity. RESULTS: These results revealed a low amount of NGF in the plasma of old subjects associated with a reduced expression of mRNA for NGF receptor trkA in peripheral lymphocytes. They also showed elevated levels of circulating interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) in the bloodstream of adult and aged subjects. CONCLUSION: Our data indicate that peripheral lymphocytes are targets for circulating NGF and suggest that changes in NGF-receptor expression on lymphocytes might be potential marker for aging lymphocytes. Copyright 2003 S. Karger AG, Basel