Answer:
Cells of the immune system are able to respond to the presence of invading organisms because they recognize the antibodies present in the invading pathogen
Step-by-step explanation:
The mechanisms of human immunity can be grouped into two broad categories: the innate or nonspecific immune system, which provides a first and general defense against any element recognized as foreign, and the acquired or specific immune system that recognizes specific threatening agents and generates a response directed against those elements. When foreign substances enter our body (bacteria, viruses, parasites, proteins from other animal or plant species, cells from other organisms - including those of human origin - and a long etcetera, all of which are given the common name of antigens) and are brought into contact with cells that are members of the immune system, the foreign element or antigen is first captured by certain types of cells that are collectively known as antigen-presenting cells. These cells would correspond to the intelligence service and their mission is to take the antigens, introduce them inside, process them and present the antigens on their surface in a fragmentary way to other cells of the immune system. This results in the activation of lymphocytes that specifically recognize the antigen and ends in the development of mechanisms that mediate the physiological function of the response, that is, the elimination of the antigen. Thus, the immune response can be functionally divided into three phases: the antigen recognition phase, the activation phase of the response, and the effector phase.