Cytotoxic human lymphocytes: from in vitro testing (1970s) to immunotherapy (1990s).

The senior author was the recipient of a contract (1-CP3-3292) from the National Cancer Institute, USA (NCI) in the early 1970s. The aim of NCI's targeted research program was the establishment of a tumour-specific human lymphocyte-mediated cytotoxicity assay. Neither lymphocyte growth factors nor monoclonal antibodies for lymphocyte typing were available. Tumour-specific populations of lymphocytes could not be maintained but their presence in ficoll-hypaque preparations of blood buffy coats or in primary cultures of tumours was clearly recognized. Another indiscriminately cytotoxic population of lymphocytes had usually overridden the tumour-specific population. In contradistinction to the ruling doctrine of the era, indiscriminately cytotoxic lymphocytes were readily found in the blood of tumour-bearing patients and healthy individuals (the senior author's lymphocytes were shown to practice indiscriminate cytotoxicity in 1971, an observation first interpreted as "immune surveillance at work" in an individual daily exposed to patients with metastatic cancers). Instead of converting the subject matter of the contract from a tumour-specific to a non-specific cytotoxicity assay, the NCI prematurely "phased it out" (but continued the project as intramural research). Nevertheless, many functions of cytotoxic lymphocytes that had become by now well established were foreshadowed during the early 1970s with the limited support of that NCI contract and funds from other sources. Here we recount those early observations; present the outlines of adoptive immunotherapy with various autologous lymphocyte populations and in a separate report in this volume give a technical description how these lymphocyte populations are prepared in the laboratory for therapeutic reinfusions into the patient.