APCs capture antigens through a process known as phagocytosis or endocytosis. Once the antigen is internalized, it is processed into smaller fragments. These fragments are then loaded onto major histocompatibility complex (MHC) molecules. There are two classes of MHC molecules: MHC class I and MHC class II. APCs primarily use MHC class II molecules to present antigens to CD4+ T-cells.
