In naive T cells PGE₂/IBMX caused a partial reduction in IL-2R and γc surface expression, but had no effect on IL-2Rβ. Surface expression of IL-2R, IL-2Rβ, and the common γ chain were examined on CD3⁺ peripheral blood T cells before and 48 hours after stimulation with anti-CD3 plus IL-2 in the presence and absence of PGE₂/IBMX. γ chain expression was determined by staining cells with 3B5. IL-2R and IL-2Rβ were detected by staining the anti-p55–PE and anti-p75–PE in combination with CD3-FITC. The percent reduction in the number of T cells expressing IL-2R chains was: 21% IL-2R, 0% IL-2Rβ, and 28% γc. The percentage of cells in each quadrant is presented adjacent to the histogram. Similar results were obtained in two additional experiments.