BCG-induced dendritic cell responses and suppression of interleukin-5 production from T cells in atopic asthmatics

Bacille Calmette-Guérin (BCG) induces potent Th1 responses with the help of interleukin (IL)-10 and IL-12 released from dendritic cells (DCs), and suppresses Th2- associated allergic reactions. However, there are still some controversies on therapeutic effects of BCG in asthmatics. This study investigated whether BCG administration to DCs suppresses IL-5 production from T cells in atopic asthmatics. DCs derived from peripheral blood of subjects were cultured with or without BCG and Dermatophagoides farinae extract. Some DCs were co-cultured with T cells in the presence of BCG or the above culture supernatants. In the atopic asthmatics, BCG significantly increased IL-10 and IL-12 production from DCs. In the presence of D. farinae extract, BCG further increased IL-10 production. BCG-induced IL-10 production was significantly higher in the atopics (n=14) than in the non-atopics (n=9). Both BCG and the BCG-treated DCs culture supernatant significantly increased IFN-gamma production from T cells. Both BCG and the supernatant from DCs+BCG+D. farinae co-cultures significantly decreased IL-5 production (all p<0.05), but the supernatant from DCs+BCG co-cultures did not. In conclusion, administration of BCG together with D. farinae extract effectively decreased IL-5 production from T cells, probably through the action of IL-10 and IL-12 released from DCs in D. farinae-sensitive asthmatics.