which of the following best explains the role of cell-to-cell communication during a response to an invasion of antigens? responses chemicals that are secreted from antigen-presenting cells then activate helper t cells. chemicals that are secreted from antigen-presenting cells then activate helper t cells. a macrophage cell engulfs a pathogen in the blood. a macrophage cell engulfs a pathogen in the blood. antigens attaching to receptors on memory b cells stimulate the memory b cells to become plasma cells. antigens attaching to receptors on memory b cells stimulate the memory b cells to become plasma cells. antigen-presenting cells engulf antigens at the first exposure.