APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -In addition to “fighting off” these pathogens, active immunity is important because it lasts a long time in the form of immunologic memory. Immunologic memory consists of B and T cells that can recognize a particular pathogen (see “Adaptive immune system").

Detailed explanation-2: -2.4. Immunologic memory is another important characteristic of adaptive immunity. It means that the immune system can remember the antigens that previously activated it and launch a more intense immune reaction when encountering the same antigen a second time (Figure 2.10).

Detailed explanation-3: -Memory is a characteristic recognized within both the innate and adaptive arms of the immune system. Although the mechanisms and properties through which innate and adaptive immune memory are induced are distinct, they collude to improve host defense to pathogens.

Detailed explanation-4: -Classical adaptive immune memory is induced by antigen presentation to specialized lymphocytes in the lymph nodes. After proliferation, elimination of the pathogen and contraction, a small number of memory lymphocytes persists to insure long-time specific memory to the target pathogen.