• bipolar disorder;
  • dexamethasone;
  • resistance;
  • T cells

Objective:  A relative resistance of immune cells to steroids has been established in patients with major depression (MD). In this study, we investigated the in vitro responsiveness of T cells to dexamethasone (DEX) of patients with bipolar disorder (BD).

Methods:  T cells of outpatients with DSM-IV BD (n = 54) and of healthy control subjects (HC; n = 29) were isolated, cultured and stimulated with phytohemagglutinin (PHA) for 72 h. The suppressive effect of graded concentrations of DEX (5 × 10−9–10−5 M) on PHA-induced CD25 (IL-2R) expression was measured by fluorescence-activated cell sorting (FACS) analysis. Data were correlated to the T-cell activation status in the peripheral blood of the same patients and to their diagnosis, current mood state, ultradian cycling pattern and current use of medication, including lithium.

Results:  T cells of patients with BD were less sensitive to DEX-induced suppressive effects as compared with T cells of HC. These data were particularly evident at 10−7 M DEX (mean % suppression ± SEM BD: 18.9% ± 3.5 versus HC: 35.8% ± 4.7, p = 0.001). We found no correlations of this relative in vitro DEX resistance of T cells neither with the previously mentioned clinical characteristics nor with the actual activation status of the T cells in the BD patients.

Conclusion:  A relative T-cell resistance to steroids, as has been observed in MD previously, may be a trait phenomenon of BD, independent of mood state.