Final answer:
Antigen-presenting cells (APCs) such as macrophages, dendritic cells, and B cells play a vital role in immune response by engulfing pathogens, processing antigens, and presenting them on their surface with MHC class II molecules to activate T cells including helper and killer T cells.
Step-by-step explanation:
The student's question pertains to the function of certain cells within the immune system that accept information from macrophages and train other lymphocytes. These cells are known as antigen-presenting cells (APCs), which include macrophages, dendritic cells, and B cells. These APCs have the critical role of capturing antigens from pathogens, processing them, and presenting them on the cell surface bound to MHC (Major Histocompatibility Complex) molecules.
T Cell Activation
T cells must be activated to combat infections. Once a macrophage phagocytizes and digests a pathogen, the antigen is presented on its surface in conjunction with an MHC molecule, marking the macrophage as an APC. Helper T cells, which can also function as APCs, are essential in activating other lymphocytes, including killer T cells, which might require further stimulation from helper T cells for activation.
Functions of APCs
APCs such as macrophages facilitate the response of T cells by binding the digested antigens to MHC class II molecules. These T cells then release cytokines that enhance the APC's phagocytic capabilities. B cells may also present antigens to T cells necessary for specific antibody responses. Lymph nodes are key locations where T cell responses are mounted against antigens presented by APCs.