Btk is required for TREM-1-induced cytokine production in mouse BMDCs. BMDCs were generated from bone marrow cells of WT, Btk^−/−, Tec^−/− and Tec^−/−Btk^−/− mice in GM-CSF-containing medium. (A) On day 3, BMDC from WT and Tec^−/−Btk^−/− mice were stained with isotype-matched (dashed line) or anti–TREM-1 (full line) mAbs and analyzed by flow cytometry. (B) On day 4, cells were incubated for 8 hours with either plate-bound isotype-matched control or plate-bound anti–TREM-1 mAbs or with PMA and ionomycin. Supernatants were analyzed by ELISA for TNF-α and MIP-2. Data are displayed as mean ± SD of at least duplicates of ELISA from duplicate cultures. Figure shows 1 representative result of 3 independent experiments. *P < .01, **P < .006 and ***P < .0001 (Student t test). iono indicates ionomycin.