Antigen presenting cells in the human immune system work with T cells to kill invading pathogens (bacteria and viruses). Antigen presenting cells will identify the pathogen and present the antigen, which is a unique protein “name tag” of the pathogen, to the T Cell so that the T cell can find and kill the pathogen. This type of communication between the antigen presenting cell and the T cell is known as... a. Direct contact b. Local signaling c. Long distance signaling d. Transduction signaling