The Effect of Poly(I:C) on the Immune System as Observed Through IL-12 Production in Dendritic Cells

Activation of dendritic cells (DCs) through chemical treatment causes release of cytokines. Original studies demonstrated that MuTu DCs, derived from the spleen of mice, responded to stimulation of Toll-like receptor 3 [TLR3] with poly(I:C) by producing IL-12. Challenges in culture of MuTu DCs led to the transition to culture and use of the DC2.4 cell line. DC2.4 cells are also murine dendritic cells but derived from the bone marrow. DC2.4 also express TLR3. To compare the response of DC2.4 cells to MuTu DCs, studies using varying doses and times of poly(I:C) exposure were conducted. In contrast to MuTu DCs, DC2.4 cells produced little to no IL-12 after 12-hour exposure to doses less than 5 µg/mL poly(I:C). Additional experiments determined what dose of poly(I:C) and exposure time was required to stimulate DC2.4 to produce larger amounts of IL-12. Other ongoing studies are investigating whether corticosterone (CORT) alters IL-12 production by DC2.4. CORT is a stress hormone known to suppress IL-12 production by the MuTu DCs. Following activation, DCs often undergo programmed cell death, or apoptosis. This occurred when MuTu DCs were stimulated with poly(I:C). Bim, a member of the Bcl-2 family of proteins, promotes apoptosis, which can be triggered through administration of chemicals such as poly (I:C). Bim was successfully detected in Human Diploid Fibroblasts (HDF), which will serve as a positive control to optimize Bim detection in DCs. Bim was also successfully detected in the DC2.4 cells. Analysis of the production of IL-12 by DCs and their subsequent apoptosis allows for greater understanding of how stress-induced chemicals affect our ability to fight pathogens