ABSTRACT
Human peripheral blood monocytes [HPBM] express HLA-DR antigen which is involved in antigen presentation processes. HLA-DR expression on HPBM is upregulated by interferon-gamma [IFN-gamma]. We looked at the effect of the glucocorticoid dexamethasone [DEX] on HLA-DR expression by HPBM cultured in serum free media using anti-human monoclonal antibodies conjugated with phycoerythin at 48 hours and under different exposure conditions. Results were assessed by immunofluorescence microscopy and flow activated cell sorter [FACS] analysis. DEX in a concentration of 1x 10[-6]M did not significantly alter HLA-DR expression on HPBM, however in the same concentration it significantly enhanced INF-gamma induced HLA-DR upregulation. Furthermore we looked at the effect of DEX on RSV infected monocytes detected by anti-RSV monoclonal antibodies conjugated with fluorescine isothiocyanate [FITC] and analysed by two colour FACS analysis. DEX at 1x10[-6]M significantly enhanced HLA-DR expression on virus infected monocytes but not non-infected cells. These data suggest that the interactions between glucocorticoids and monocyte immunoregulatory functions are more complex than previously thought and may not always be of immunosuppressive nature