Depressed production of beta-defensins from mouse splenic dendritic cells following thermal injury and its influence on susceptibility to infection

Purpose: Beta-defensins (BDs) and dendritic cells (DC) have been described as major effectors on host antimicrobial innate immunities. In the present study, the ability of DC to produce BDs was explored using DC from normal mice and full-thickness (FT)-burned mice.

Methods: DCs were isolated from spleens of mice, and 1 × 10⁶ cells/ml of them were cultured with LPS or SAC. Culture fluids harvested 24 h after cultivation were assayed for BD1 and BD3 and antibacterial activity (colony-counting, Pseudomonas aeruginosa). Also, DCs were tested for BD mRNAs by RT-PCR.

Results: Sixty-five percent of the bacterial killing activity was shown by the culture fluids of splenic DC from normal mice, while only 15 % killing activity was shown by the culture fluids of splenic DC from FT-burned mice. X-irradiated NOD SCID IL-2rγ^null mice inoculated with splenic DC from FT-burned mice showed increased susceptibility to P. aeruginosa infection compared to those from normal mice. Mice splenic DC expressed BD1 mRNA constitutively and expressed BD3 mRNA after stimulation. These BDs were produced by mice splenic DC. As compared with DC from normal mice, DC from FT-burned mice produced decreased amounts of BD1 and BD3 in their culture fluids.

Conclusions: These results indicate that (1) DC from spleens of mice have an ability to produce BDs, and (2) the production of BDs by DC is influenced strongly by thermally injured stress. Since FT-burned mice are susceptible to P. aeruginosa infection, BDs produced by DC may play an important role on the host’s antibacterial resistance.