"Experiments of Nature" and the New Era of Immunology: an historical perspective.

This review of the events leading to the New Era of Immunology focuses on the important leads provided by the Experiments of Nature. Not only did they provide the path that led to our present knowledge of the ontogeny of the immune system, but also to an entirely new perspective of lymphocytic malignancies. The power of taking clinical clues to the laboratory to conduct experiments not otherwise envisioned and then returning with that information to impact the clinical problem that motivated the studies is elaborated. Finally, the ongoing utility of this approach is emphasized.