Antigen-presenting cell uptake machinery

The antigen-presenting cell (APC) uptake machinery is a collective term for the diverse array of receptors and endocytic pathways employed by professional APCs, such as dendritic cells, macrophages, and B cells, to internalize exogenous antigens. This machinery includes several specialized receptor families, most notably C-type lectin receptors (e.g., DEC-205, DC-SIGN, and the Mannose Receptor), Fc receptors, and scavenger receptors, which recognize pathogen-associated molecular patterns or opsonized particles. Once internalized via mechanisms like receptor-mediated endocytosis, phagocytosis, or macropinocytosis, antigens are directed into the endolysosomal pathway for proteolytic degradation into peptides. These peptides are subsequently loaded onto MHC class I or II molecules for presentation to T cells, a critical step in the initiation of adaptive immune responses. In therapeutic contexts, this machinery is targeted by vaccines and immunotherapies to enhance antigen delivery and immune activation. For example, antibody-antigen conjugates target specific uptake receptors like DEC-205 to ensure efficient T-cell priming, while lipid nanoparticle-based mRNA vaccines rely on these pathways for cellular entry and subsequent protein expression. Dysregulation or evasion of the APC uptake machinery is a common feature in cancer and chronic infections, where reduced antigen internalization contributes to immune subversion. Conversely, over-activation or inappropriate targeting of these pathways can lead to hypersensitivity or autoimmune reactions.

Other names

Antigen uptake systemAPC internalization pathwaysEndocytic machinery of professional APCsPhagocytic machineryAntigen capture machinery

Facilitation of antigen internalization via receptor-mediated endocytosis, phagocytosis, or macropinocytosis, followed by intracellular processing and MHC-mediated presentation to T cells.