Thermal regulation of dendritic cell activation and migration from skin explants

Dendritic cells (DCs) in the skin rapidly take up antigen and migrate out of the skin to draining lymph nodes for antigen presentation. As a result, these cells play an important role in generating specific immune responses against infectious agents that enter the skin and against antigens delivered as vaccines. Previous efforts revealed that fever-like elevations in body temperature enhance antigen-dependent immune responses initiated at the site of the skin and stimulate the migration of epidermal DCs to draining lymph nodes. Collectively, these data have led to the hypothesis that the activation of epidermal DCs is sensitive to physiological thermal stimuli. In this study, ear skin explants derived from BALB/c mice were either maintained at 37 degrees C or incubated at 40 degrees C for the first 6.5 h before being placed at 37 degrees C. This heating protocol altered the density and morphology of the epidermal DCs in a manner suggestive of an increased kinetics of activation-associated DC migration. Flow cytometric analysis of the emigrated cells also indicated that mild heating enhanced the migration kinetics of DCs and increased the DC expression of MHC class II and the activation marker CD86. Importantly, these migrated cells displayed higher stimulatory capacity in a mixed lymphocyte reaction compared to those of controls. Overall, these results suggest that mild thermal stimuli can enhance DC activation and function and that strategic applications of heat could enhance the potency of vaccines consisting of relatively weak antigens, such as cancer vaccines.