Stimulation of human B lymphocyte differentiation by the neuropeptides substance P and neurokinin A.

Substance P (SP) at a concentration of 10(-7) M significantly increased the number of IgG-producing cells induced by the polyclonal activator Staphylococcus aureus protein A (SpA) in 11 out of 22 cultures of enriched human blood B lymphocytes, in nine cultures SP did not significantly affect the SpA response and in three cultures IgG secretion was decreased in the presence of SP. Stimulation by SP was observed in cultures at days 6 and/or 8. In 3 out of 4 cell cultures depleted of monocytes SP did not affect the cell response to SpA stimulation. SP antagonists inhibited the enhancing effect of SP on B-cell antibody secretion induced by SpA. SP alone did not stimulate B lymphocytes. Neurokinin A (NKA) had similar effects as SP and enhanced the IgG secretion induced by SpA in 5 out of 9 experiments, in two experiments was inactive, and in one decreased the IgG secretion. The effect of SP and NKA on B lymphocytes suggest that the neuropeptides interact with the regulation of the immune response.