The effect of dexamethasone(DEX) on delayed-type hypersensitivity(DTH) reactions and antibody responses to various concentrations of sheep red blood cells (SRBC), and of polyvinylpyrroridone(PVP), graft-vs-host reaction were evaluated. DEX treatment(lOOpg/mouse, 1.p, b.I.d.) was begun 1 daybefore immunization or cell transfer and continued until challenge with antigen or throughout experiments. The treatment with DEX inhibited DTH and antibody responses to high, low and intermittent doses and markedly inhibited GVH reactivity of thymus, lymph node and spleen cells. DEX markedly inhibited antibody response to high(25pg/mouse) and low(0.025pg/mouse) doses of PVP, but not to intermit-tent dose(0.25pg/mouse) which is optimal immunizing dose of PVP in mice.
The ability of DEX to inhibit the immune suppression mediated by different types of murine T sup-pressor cell was also evaluated. The activity of suppressor cells induced by UVB irradiation, :: dinitrobenzene sulfonic acid(DNBS) injection and inoculation with a high dose of SRBC was evaluated after adoptive transfer to naive syngeneic recipients. DEX was administered to recipients b. i. d. at the dose of 100pg/mouse, beginning I day before the adoptive transfer of UVB?, DNBS? or .SRBC?tolerized spleen cells (1 X10´/mouse) continuing until challenge. DEX treatment abrogated the expression of DNBS?induced, Lyt?2 , T suppressor cells and stimulated contact sensitivity to dinitrofluorobenzene(DNFB) in adoptive transfer experiments. In contrast, the Lyt?1´´ T suppressor cell activity induced by UVB irradiation and the Lyt?2+ T-suppressor cell-mediated unresponsiveness induced by inoculation with a high dose of SRBC were refractory to DEX treatment. UVB-induced suppression of both con-tact sensitivity to DNFB and DTH response to SRBC could be transferred into recipients. These results indicate that T suppressor cell populations differ markedly in their susceptibility to modulation by DEX treatment, illustrating the diversity of suppressor cell mechanisms operating different in immune states. This also suggests that meaningful application of immunotherapeutic modulation may re-quire a precise understanding of the property of suppressor cell suhpopulations involved in a specific immune response before reliable ther apy can be achieved.
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