Neonatal chlorpyrifos administration elicits deficits in immune function in adulthood: a neural effect?

Neural input plays a key role in the establishment of immune function, and environmental agents or drugs that interfere with the development of the ne rvous system elicit corresponding immunologic deficits. In the current stud y, we gave neonatal rats the widely used organophosphate pesticide, chlorpy rifos (CPF), and determined the immediate and long-term effects on T-lympho cyte function. Exposure of neonatal rats to 1 mg/kg of CPF daily on postnat al days (PN) 1-4 had no immediate effect (PN5) on T-cell mitogenic response s to concanavalin A challenge. However, once the animals reached adulthood, T-cell responses were significantly impaired. There were no deficits in ba sal T-cell replication rates, implying that the adverse effect of CPF expos ure was specific to mitogenic activation. Treatment during a later neonatal period (PN11-14) elicited similar deficits in adulthood. CPF administratio n leads to inhibition of cholinesterase, and a cholinergic connection is su pported by the fact that the results seen here correspond to those seen wit h a direct cholinergic stimulant (nicotine) administered during gestation o r adolescence. These results indicate that exposure to CPF during a develop mental period in which this organophosphate pesticide is known to produce l asting changes in neural function, elicits corresponding, long-term deficit s in immune competence. (C) 2001 Elsevier Science B.V. All rights reserved.