Hemispheric asymmetry in the effects of cerebral cortical ablations on mitogen-induced lymphoproliferation and plasma prolactin levels in female rats

Female rats were subjected to unilateral left or right, bilateral, or sham ablation of the cerebral cortex. Eight weeks after surgery, the rats were sacrificed by decapitation and spleen cells were grown in culture for 96 h in the presence or absence of the T-cell mitogen concanavalin A or the B-cell mitogen lipopolysaccharide. Mitogenesis was determined by the addition of [ 3H]thymidine 24 h prior to harvesting. Both T- and B-cell mitogenesis were significantly depressed in subjects bearing cortical ablations in the right hemisphere, whereas left hemisphere ablation was without reliable effect. Prolactin in plasma collected at sacrifice was elevated in rats bearing right but not left hemisphere ablation and was significantly negatively correlated with both T- and B-cell immune responses. These results demonstrate a lateralized modulatory influence of cerebral cortex on immune function in female rats and they implicate elevated prolactin levels as a possible mediator of this effect.