Final answer:
Adaptive immunity allows for the recognition of specific antigens on pathogens and infected cells, with B and T lymphocytes playing key roles in the specific and memory-equipped response.
Step-by-step explanation:
The type of immunity capable of identifying infected body cells as well as pathogens in the blood upon exposure to specific antigens is known as adaptive immunity. This system involves highly specialized cells, including B and T lymphocytes, that can recognize foreign antigens and mount a precise immune response.
The adaptive immune response develops an almost unlimited variety of receptors, up to 100 trillion, to recognize and respond to a vast array of pathogens. This functional diversity is achieved through a sophisticated mechanism, explored in the 1970s and 1980s, that allows for a wide range of antigen receptor generation without the need for corresponding gene for each specificity.
Adaptive immunity includes both the cell-mediated immune response, controlled by T cells, and the humoral immune response, driven by B cells and antibodies. These responses take more time to develop than the innate immune response, but are incredibly specific to the pathogen and have the remarkable feature of immunological memory. Memory cells formed after an initial exposure to a pathogen enable a rapid and potent response upon reexposure, usually before the pathogen can cause disease.