Figure 4: (A) Up-regulation of surface biomarkers on bone marrow-derived DC (BMDCs) by rRBD. BMDCs from C57BL/6 were collected and treated with GM-CSF at day 0 and 3. At day 6, rRBD (1 μM final concentration) was added, and 18 hours later DCs were collected for surface biomarkers expression (including CD40, CD80, CD86, and MHC II) by flowcytometry. Samples were divided into groups treated or not treated with polymyxin B (PMB) to assess the influence of residual LPS contamination. Surface marker signaling was normalized by calculating the ratio of mean of fluorescence intensity (MFI) between medium control and treatments. (B) Cytokines secretion from BMDC treated with tcdA rRBD. After BMDCs were treated with rRBD at day 6 for 18 hours, culture supernatants were collected and analyzed for their cytokine profiles using specific cytokine ELISA: IL-6, IL12-p40, and TNF- α.