Antigen-presenting cell and T-cell activation pathway

The **antigen-presenting cell and T-cell activation pathway** refers to the series of coordinated cellular and molecular interactions that trigger adaptive immune responses. Antigen-presenting cells—chiefly dendritic cells, macrophages, and B cells—capture, process, and present antigenic peptides to T cells via major histocompatibility complex (MHC) molecules[1][8]. Activation of T cells requires two principal signals: (1) the T-cell receptor (TCR) recognizes the antigen peptide-MHC complex, and (2) co-stimulatory molecules (such as CD80 or CD86 on the APC interacting with CD28 on the T cell) deliver a required second signal for full T-cell activation[1][6][3]. Without both signals, T cells become anergic or tolerant[3]. Signaling cascades downstream of TCR and co-stimulatory engagement activate kinases, phosphatases, and transcription factors, leading to T-cell proliferation, cytokine production, and effector function[5][7]. This pathway is central to effective immunity against infection, tumor surveillance, and is targeted in immunotherapy and autoimmune disease treatments[6][4][5].

Other names

antigen presentation pathwayAPC/T cell activationAPC–T cell interaction