We owe to Clemens Von Pirquet the initial immunoclinical and immunopathological description of anergy (1). Anergy has been generally defined as: "The state of an organism that has lost the ability to specifically react with an antigen to which it was previously sensitized." At this point, we must emphasize that we are focusing on abnormalities of the secondary or "memory" phase of the immune response. Commonly, anergy is demonstrated by the inability to mount a delayed-type hypersensitivity (DTH) response to a battery of recall antigens (cutaneous anergy). For many years, the physiopathology of anergy remained unknown, but the probable mechanisms related to the onset and natural history of anergy were linked to a broad defect in cell-mediated immunity (CMI).