Quantitative analysis of the neuroendocrine-immune axis

The effects of exogenous corticosterone and restraint stress on the number and percentage of lymphocyte subpopulations in the spleen and thymus were evaluated. The data were used to generate linear models that describe the relationship between these parameters and the area under the corticosterone concentration vs time curve (AUC). Comparison of the models revealed that the number of nucleated cells in the spleen was decreased similarly by exogenous corticosterone and restraint (at equivalent corticosterone AUC values). However, exogenous corticosterone caused a greater decrease in cell number in the thymus than it did in the spleen. Corticosterone preferentially depleted CD4+CD8+ cells in the thymus, whereas the same corticosterone exposure produced by restraint stress did not. In the spleen, cell number for all major cell types was decreased by both treatments, but there were minor differences in the change in percentage of some subpopulations induced by exogenous corticosterone as compared to restraint. The models derived here provide quantitative data that indicate the magnitude of corticosterone and stress-induced effects on lymphocyte populations in the spleen and thymus. These results have mechanistic implications, and they may be useful in future efforts to extrapolate from mouse to human by completing a risk assessment parallelogram.