Triggering of CD300a and CD300c increases type I IFN and IRF7 expression by pDCs. (A) pDCs were cross-linked with 10 μg/mL CMRF-35 mAb or CMRF-81 control antibody (10 μg/mL; Ctr IgG) for 30 minutes, then stimulated with CpG. IFN-α mRNA was analyzed by real-time PCR in pDCs cultured for 48 hours. Data are representative of 3 experiments. (B) IFN-α levels in supernatants collected from pDCs after CMRF-35 cross-linking and cultured for 48 hours was measured by ELISA (from left to right). Cross-linking with BDCA-2 mAb or non–cross-linking of pDCs were used as control. Data are from 1 of the 3 experiments. pDCs were cross-linked with 10 μg/mL CMRF-35 mAb for 30 minutes, then stimulated with CpG for 15, 48 hours. mRNA from IRF7 (C) and MyD88 (D) was analyzed by real-time PCR. Data were representative of 3 experiments. Error bars represent SEM.