Final answer:
The immature phenotype of DCs is marked by a lower expression of co-stimulatory molecules and MHC class I and II receptors, making them less effective at inducing T-cell responses until they receive maturation signals and upregulate these molecules.
Step-by-step explanation:
The immature phenotype of dendritic cells (DCs) is characterized by lower expression levels of co-stimulatory molecules and major histocompatibility complex (MHC) class I and II bioreceptor molecules when compared to their mature counterparts. Immature DCs are essential in initiating an immune response, as they are potent antigen-presenting cells that capture antigens and migrate to lymphoid organs. Upon receiving maturation signals, often through interactions with pathogens or inflammation, immature DCs undergo a maturation process involving upregulation of co-stimulatory molecules such as CD80, CD86, and MHC molecules, which are critical for T-cell activation. This maturation also includes increased production of cytokines and chemokines important for immune responses, and the activation of signaling pathways like mitogen-activated protein kinase and nuclear factor-kB (NF-kB), as seen in studies involving the impact of nanoparticles on DC maturation for cancer immunotherapy.