Inhibitor of differentiation 3 (Id3) regulates interleukin (IL)-5 production in natural helper cells (NHCs). A, Representative flow cytometry for the gating strategy of fat-associated lymphoid cluster NHCs. Live, CD45+ cells were gated for lineage-negative markers, then for Sca1+ CD117+ cells. CD44, CD90, and T1/ST2 expression on Sca1+ CD117+ cells from Id3+/+Apoe−/− mice (open histograms) or T1/ ST2 from Id3−/−Apoe−/− mice (green-shaded histogram). Fluorescence-minus-one control, gray-shaded histograms. B, Top, Representative flow cytometry of NH cells, CD4+ T cells, and mast cells (MC) from Id3+/+Apoe−/− or Id3−/−Apoe−/− mice stained for intracellular interferon-γ (IFNγ) and IL-5 after IL-33 stimulation and (bottom) quantification of IL-5 production. Results are expressed as individual mice from 2 independent experiments performed in duplicate. C, Luciferase activity (top) and protein expression of Id3 and β-tubulin (bottom) in lymphoid cells cotransfected with IL-5 promoter-reporter and either empty vector (control) or Id3. Data are from 3 independent experiments performed in duplicate. *P<0.05.