Carma1, but not Card9, is required for NK-cell receptor signaling. IL-15–expanded NK cells from Card9-deficient (A) or IL-15–expanded NK cells from Carma1-deficient (B) or control mice were stimulated with plate-bound anti–NK-cell receptor antibodies or PMA/Iono as indicated for 24 hours. Cytokine release was measured by ELISA. Data are means plus or minus SD of triplicate samples and representative of 3 independent experiments.