ABSTRACT

The origin of modern tumor immunology dates back to the 1950s, when several groups of investigators in the USA and Europe demonstrated a) that the immune system of inbred mice and rats can recognize antigens expressed by tumor cells induced by chemical carcinogens; b) that such recognition results in rejection of a subsequent challenge of the same tumor in previously immunized animals; and c) that immune cells but not antibodies can mediate this reaction (Baldwin, 1955; Prehn and Main, 1957; Klein et al., 1960; Old et al., 1962). In the classical papers by Prehn, Klein and Old, most of the problems that pervaded the field in the following years (some of which are still to be solved) were clearly identified, with the possible exception of the escape of tumors from the immune response that became apparent later on, when tumor-infiltrating T lymphocytes could be functionally studied in vitro (Whiteside et al., 1986).