The polysaccharides of Ganoderma lucidum (Reishi) possess immunomodulation activities; however, their mode of molecular action in regulating each cellular subset in the immune system is still not clear. Here, we investigate the function of the main polysaccharide fraction of Reishi (Reishi-F3) in B lymphocyte activation/differentiation. We find that Reishi-F3 causes mouse splenic B cell activation and differentiation to IgM-secreting plasma cells, and the process depends on Reishi-F3-mediated induction of Blimp-1, a master regulator capable of triggering the changes of a cascade of gene expression during plasmacytic differentiation. In human peripheral B lymphocytes, although Reishi-F3 fails to induce their activation, it is able to enhance antibody secretion, which is associated with Blimp-1 mRNA induction. The function of Reishi-F3 depends on the Toll-like receptors TLR4/TLR2 as neutralizing antibodies against TLR4/TLR2 block Reishi-F3-mediated induction of Blimp-1 mRNA and Ig secretion. We have shown that interaction of Reishi-F3 with TLR4/TLR2 followed by signaling through p38 MAPK is involved in the induction of Blimp-1 mRNA, whereas signaling through ERK, p38 MAPK, JNK, and IKK complex is involved in Reishi-F3-mediated Ig secretion. Furthermore, the differential mechanism of Reishi-F3 in mouse and human B cell activation is probably due to the presence of Blimp-1 regulatory site in human CD86 promoter. These results establish the signaling and molecular mechanisms of Reishi-F3 on promoting antibody secretion.

Some polyacetylenes from the plant Bidens pilosa have been reported to treat diabetes. In this study, we report that the cytopiloyne from B. pilosa, which is structurally different from the above-mentioned polyacetylenes and inhibits CD4+ T cell proliferation, effectively prevents the development of diabetes in nonobese diabetic mice as evidenced by a normal level of blood glucose and insulin and normal pancreatic islet architecture. Cytopiloyne also suppresses the differentiation of type 1 Th cells but promotes that of type 2 Th cells, which is consistent with it enhancing GATA-3 transcription. Also, long-term application of cytopiloyne significantly decreases the level of CD4+ T cells inside pancreatic lymph nodes and spleens but does not compromise total Ab responses mediated by T cells. Coculture assays imply that this decrease in CD4+ T cells involves the Fas ligand/Fas pathway. Overall, our results suggest that cytopiloyne prevents type 1 diabetes mainly via T cell regulation.

B lymphocyte-induced maturation protein-1 (Blimp-1) is a transcriptional repressor that plays an important role during plasmacytic differentiation and is expressed in normal and transformed plasma cells. We here investigated the importance of continuous Blimp-1 expression. We found that knockdown of Blimp-1 expression by lentiviral vector-delivered short hairpin RNA causes apoptosis in multiple myeloma cell lines and plasmacytoma cells, indicating that continued expression of Blimp-1 is required for cell survival. We examined the mechanism underlying Blimp-1 knockdown-mediated apoptosis and found that the Blimp-1 knockdown neither reversed the phenotypic markers of plasma cells nor caused cell cycle arrest. Instead, our results show that knockdown of Blimp-1 induced the proapoptotic protein Bim, reduced the antiapoptotic protein Mcl-1, and activated caspase-9 and caspase-3. We further link apoptosis in transformed plasma cells mediated by proteasome inhibitors, the effective therapeutic agent for multiple myeloma patients, with reduced expression of Blimp-1. Lastly, we show that Blimp-1-dependent cell survival may act downstream of IFN regulatory factor 4 (IRF4) because IRF4 knockdown leads to down-regulation of Blimp-1 and apoptosis in multiple myeloma cells and plasmacytoma cells. Together, our data suggest that Blimp-1 ensures the survival of transformed plasma cells.

Bidens pilosa is claimed to be useful for immune or anti-inflammatory disorders; however, little scientific evidence has been published concerning its function. In this paper, immune disease mouse models were used to study the function of a butanol fraction of B.pilosa. We demonstrated treatment with the butanol fraction of B.pilosa ameliorated Th1 cell-mediated autoimmune diabetes in nonobese diabetic (NOD) mice but caused deterioration of Th2 cell-mediated airway inflammation induced by ovalbumin (OVA) in BALB/c mice. We next showed that Th2 cytokines (IL-4 and/or IL-5) increased but Th1 cytokine (IFN-gamma) decreased following injections with the butanol fraction of B.pilosa in both mouse strains. Accordingly, Th2 cytokine-regulated IgE production in mouse serum increased following treatment with this fraction. Finally, we found that the butanol fraction of B.pilosa inhibited Th1 cell differentiation but promoted Th2 cell differentiation. Taken together, the butanol fraction of B.pilosa has a dichotomous effect on helper T cell-mediated immune disorders, plausibly via modulation of T cell differentiation.