(b d c e a)
Work Step by Step
The following are the steps for cell-mediated immune reactions: 1. Antigen-presenting cells (macrophages and dendritic cells) phagocytize pathogens, ingesting and degrading them into pieces which are transported to the surface of the cell. 2. Some pieces of the pathogen’s antigens are processed by inserting them into the antigen-presenting cell’s membrane and are held in place by class II major histocompatibility complex (MHCII) proteins. 3. T cells bearing the corresponding receptor for the presented antigen bind to it and become activated only if the appropriate MHC is also present. 4. Activated T cells are stimulated to divide and differentiate into different types of T cells, including memory cells. 5. Differentiated T cells include T helper, delayed hypersensitivity, cytotoxic, and memory T cells that all have different immunological functions depending on the antigen presented.