Dendritic cell licensing refers to the process by which dendritic cells are activated and matured by signals from other immune cells or from the environment. The process of licensing enables dendritic cells to effectively stimulate T cells and initiate an adaptive immune response. Dendritic cells that are not licensed, or immature dendritic cells, are not as effective at activating T cells and may even induce immune tolerance, which can be detrimental in the context of infectious diseases or cancer. Licensing can occur through various mechanisms, such as the recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs) on dendritic cells, or through the interaction of dendritic cells with activated T cells, which can provide a feedback loop to further enhance dendritic cell activation. Once licensed, dendritic cells upregulate the expression of co-stimulatory molecules and cytokines, which are necessary for effective T cell activation and differentiation. In this way, dendritic cell licensing plays a critical role in initiating and coordinating the adaptive immune response against invading pathogens or cancer cells.