Deletion of microRNA miR-223 increases Langerhans cell cross-presentation.

Langerhans cells (LCs) are skin-residential dendritic cells that regulate skin immunity. MicroRNAs (miRNAs) are key regulators in the control of biological functions in a variety of cell types. Deletion of all miRNAs interrupts the homeostasis and function of epidermal LCs. However, the roles of individual miRNAs in regulating LC development and function are still completely unknown. MiRNA miR-223 is especially expressed in the myeloid compartment. Here, we reported that miR-223 is highly expressed in freshly isolated epidermal LCs, and tested whether miR-223 regulates LC development and function using miR-223 knockout (KO) mice. We found that the number, maturation, migration and phagocytic capacity of LCs were comparable between miR-223KO and wild-type mice. However, lack of miR-223 significantly increases LCs-mediated antigen-specific CD8(+) T cell proliferation in vivo and in vitro, while LCs from KO and WT mice showed comparable stimulation for antigen-specific CD4(+) T cells. Our data suggest that miR-223 negatively regulates LC cross-presentation, but may not be required for normal LC homeostasis and development.