Effects of neurointermediate pituitary lobectomy on humoral and cell-mediated immune responses in the rat

Objective: Chronic stress is characterized by an increased activity of the hypothalamic-pituitary-adrenocortical axis and decreased humoral and cell-mediated immune responses. In the rat, corticosterone is the principal natural immune suppressor. Neurointermediate pituitary lobectomy ( NIL) in rats induces diabetes insipidus and protracted increases in basal adrenocorticotropin and corticosterone plasma levels, a situation that resembles chronic stress. In this paper, we evaluated the effects of NIL on humoral (hemagglutinin titers and foot-pad swelling to sheep red blood cells-SRBC) and cell-mediated immune responses ( contact hypersensitivity to dinitrochlorobenzene). Methods: The studies were conducted on NIL Wistar rats (body weight 150-200 g) 3 weeks after surgery. For comparisons, nonoperated control rats were used. Results: NIL resulted in an increased water intake. Body weight gain and adrenal, thymus, and spleen weights were within the range of nonoperated controls. Eight days after SRBC immunizations a second SRBC injection into the footpad resulted in a decreased swelling response in NIL rats. The hemagglutinin titers were also reduced in the NIL rats. Conclusions: These results indicate that: ( 1) NIL reduces humoral immune responses and decreases the cell-mediated immune response; ( 2) the immune alterations are most likely due to the increased activity of the hypothalamic-pituitary-adrenocortical axis induced by NIL, and ( 3) NIL animals constitute a valuable paradigm to study hypothalamic-pituitary-immune interactions. Copyright (C) 2004 S. Karger AG, Basel.