IFN-beta treatment inhibits IFN-alpha, IL-6, and TNF-alpha secretion by activated pDCs. pDCs were separated from the same MS/CIS patients before (pretreatment) and after a 3-month course of treatment (IFN-beta treatment) with recombinant human IFN-beta-1b (subcutaneous, n = 8) or recombinant human IFN-beta-1a (intramuscular, n = 6). The average age of patients was 36.3 years; 9 females and 5 males. pDCs were activated in vitro with TLR9 agonist for 16 hours. (A) IFN-alpha2, (B) IL-6, and (C) TNF-alpha were measured in the same cell supernatants by MILLIPLEX Multi-Analyte Profiling as described in Patients and Methods. IFN-beta-treated patients had decreased levels of IFN-alpha2 (mean ± SEM = 1,498 ± 372 pg/ml vs 2,917 ± 535; p = 0.0246), IL6 (33 ± 6 pg/ml vs 74 ± 11; p = 0.0012), and TNF-alpha (117 ± 17 pg/ml vs 317 ± 63; p = 0.0021) when compared to untreated patients. SEM = standard error of the mean.