Antigen presentation machinery

Antigen presentation machinery refers collectively to the cellular processes and molecular components responsible for displaying peptide fragments—derived from intracellular or extracellular proteins—on major histocompatibility complex (MHC) molecules at the cell surface. This process is essential for immune surveillance by CD8^+^ and CD4^+^ T cells. In cancer, tumor antigens—including neoantigens generated by mutations—are presented on MHC class I molecules (also called HLA-I in humans), allowing cytotoxic T lymphocytes to recognize and destroy malignant cells. Effective anti-tumor immunity requires both efficient uptake/cross-presentation by dendritic cells for priming naïve CD8^+^ T cells and direct display on tumor cells for effector recognition. Tumors can evade immunity through downregulation or loss of key components in this pathway—including reduced expression of MHC molecules or defects in peptide processing—which impairs detection by cytotoxic lymphocytes. Enhancing this system is a major therapeutic strategy in cancer immunotherapy; approaches include stimulating interferon signaling pathways that upregulate antigen processing genes or using checkpoint inhibitors that release brakes on existing anti-tumor responses[1][2][3]. Biomarkers such as TIGS integrate measures of both tumor mutational burden and efficiency of antigen presentation as predictors for response to immunotherapies like checkpoint blockade.

Other names

Antigen processing and presentation pathwayMHC class I antigen presentationMajor histocompatibility complex class I pathwayHLA-I antigen presentation machinery

Enhancement of antigen processing and MHC class I/II expression to increase tumor visibility to T cells[1][2][3]; Inhibition of immune checkpoints to allow T cell recognition of presented antigens[3][4]