The B-cell activating factor (BAFF) is essential for proper B-cell development. Cells of the innate immune system including macrophages and dendritic cells are the primary source of BAFF. The BAFF protein has two forms, soluble and membrane bound. The membrane bound form of BAFF can become soluble following furin convertase-mediated digestion.. Through microarray analysis comparing the gene profile of Th9, Th2 and T-regulatory cells we found that expression of the gene encoding BAFF (Tnfsf13b) was enriched within the Th9 subset. Using qPCR, intracellular staining, and ELISA, we have confirmed that Th9 cells express BAFF both at the mRNA and protein level. Although Tnfsf13b is expressed at the greatest level in Th9 cells, Th2 cells also express detectable mRNA. Yet, BAFF secretion is only detected in supernatants from Th9 cells. We hypothesized that the absence of soluble BAFF in Th2 supernatants could be due to a difference in the level of Furin expressed by Th9 and Th2 cells. Indeed Th9 cells express a higher level of Furin compared to Th2 cells. Moreover, blocking Furin activity diminishes BAFF secretion from Th9 cells. Together, these data suggest that BAFF production from Th9 cells results from the coordinated expression of both the gene encoding BAFF, and the enzyme required to generate soluble BAFF. Furthermore, Th9 cells may be an important source of BAFF during the development of humoral immunity.
- Copyright © 2013 by The American Association of Immunologists, Inc.