Effects of monocytes from human neonates on lymphocyte transformation

Abstract

Adherent cells (approximately 75% monocytes, 25% lymphocytes) obtained from neonates and from adults were studied to compare their effects on mitogen-induced lymphocyte transformation. The response of autologous lymphocytes to concanavalin A (Con A) was enhanced significantly by adherent cells from neonates and from adults. Whereas the addition of 2-mercaptoethanol (2-ME) did not enhance the response of unseparated peripheral blood mononuclear cells or fully restore the response of adherent cell-depleted lymphocytes from neonates, both of these effects were observed when 2-ME was added to cell preparations from adults. In fact, the response to Con A of lymphocytes from adults was significantly greater in the presence of 2-ME than in the presence of autologous adherent cells. Equivalent enhancement of the response to Con A was observed when adherent cells from neonates were added to lymphocytes from adults or when adherent cells from adults were added to lymphocytes from neonates.

Adherent cells from neonates consistently inhibited the autologous lymphocyte response to the specific B-cell mitogen, NWSM, a water-soluble extract of Nocardia opaca. Lymphocytes from five out of nine neonates failed to respond to NWSM unless adherent cells were depleted. The presence of adherent cells did not prevent the response of lymphocytes from any of the eight adults tested. This difference in response to NWSM between lymphocytes from neonates and adults was significant. Inhibition of the response of autologous lymphocytes to NWSM by adherent cells from adults was of lesser magnitude and could be demonstrated consistently only when 2-ME was added to adherent cell-depleted lymphocyte preparations. We conclude that the effects of adherent cells which were observed were due to monocytes. The enhancing effect of monocytes from adults on lymphocyte response to Con A could be replaced by 2-ME, whereas this was not true for neonates. In contrast to their effects on response to Con A, monocytes from neonates inhibited the response to NWSM more consistently and to a greater degree than did monocytes from adults.