Professional antigen-presenting cell (APC)

Professional antigen-presenting cells are a functional class of immune cells—consisting mainly of dendritic cells, macrophages, and B cells—that express both MHC class I and class II molecules and specialized co-stimulatory signals required for activation of naïve T cells. Their primary role is to capture and process antigens, then present fragments via MHC class II to helper (CD4+) T cells or MHC class I for cytotoxic (CD8+) T cells, igniting adaptive immune responses. These cells are essential for the initiation, regulation, and specificity of immune reactions against pathogens, tumors, and in tolerance, and form critical points of intervention for immunotherapy and vaccine development. The term "professional" denotes cells whose primary function is antigen presentation, distinguishing them from many other cell types that can present antigens only under certain conditions. However, "Professional antigen-presenting cells" refers to a grouping of cell types, not a discrete molecule or receptor, and precise targeting usually requires specification of the cell subtype or the molecular machinery involved (e.g., MHC II, co-stimulatory ligands).

Other names

Antigen-presenting cellaccessory cellpAPC

Enhancement of antigen presentation to T cells; Stimulation of co-stimulatory signals for full T cell activation; Modulation or blockade of inhibitory signals (e.g., PD-1/PD-L1 pathway); Induction of tolerance or immune activation via cytokine secretion