A small subpopulation of dendritic cells secrete IL-2 protein.

<p><b>A:</b> CD11c⁺ dendritic cells contain IL-2 protein. DCs were stained for intracytoplasmic IL-2 as in materials and methods. Panels show FACS contour plots of BMDCs stained with anti-IL-2 (right) or isotype control antibody (left). The experiments were repeated with similar results. <b>B:</b> Progressive purification of CD11c⁺ dendritic cells enriches for IL-2 producing cells. The frequency of spontaneous IL-2 secreting BMDCs was measured by IL-2 ELISPOT assay as in materials and methods. Bars show mean ± SE of % IL-2-producing cells in triplicate samples of unpurified, 1X and 2X MACS-purified CD11c⁺ BMDCs. Statistical analysis was by one-way repeated measures ANOVA and Tukey's test for all pairwise multiple comparison procedure. <b>C:</b> Dendritic cells were doubly-purified and the percentage of IL-2-producing bone marrow-derived DCs ranged from 0.7 to 2.4% (N = 7), and the percentage of IL-2-producing splenic-derived DCs ranged from 1.2 to 2.0 (N = 3).