Studies have been performed using two subcutaneously implanted mouse tumor models to investigate the immunotherapeutic potential of lymphokine-containing culture supernatants from long-term human lymphoblast cell cultures. Human lymphoblastoid cell line, RPMI 1788, was used as a cell culture source of lymphokines. Supernatants were removed from cultures at the stationary phase of growth and concentrated on Amicon filters retaining molecules above 10,000 Daltons. This concentrate was applied to a Sephadex G-25 column, equilibrated with ammonium bicarbonate buffer, for removal of salts and dye from the culture medium. The effluent was lyophilized and reconstituted for use in further purification by affinity chromatography and SDS-PAGE gels. Such preparations were used to inject DBA/2 mice bearing subcutaneous L-1210 tumors. In addition, the B-16 melanoma was used as a model of a solid tumor in C57Bl/l mice. Animals were treated intralesionally and intraperitoneally with lymphokines containing preparations and control solutions. Tumors growing subcutaneously were susceptible to lymphokine-induced inflammation-mediated regression without additional therapy. In the study of L-1210 subcutaneous tumors, reduction in tumor size was followed by complete regression, prolonged survival, immunity to additional inoculation, and cures in 20--40% of the treated mice. Tumor regression and prolongation of survival were also noted in mice bearing B-16 melanomas. These studies support the use of mouse tumors as bioassays for antitumor inflammatory activity of human lymphokine preparations and help to quantitate their potential use in human tumor immunotherapy.

Over the past six years our studies have involved the use of cell-free supernatants derived from long term cultures of human and mouse lymphoblast cellThe properties of lymphocyte mediators (lymphokines) have been extensively reviewed 4 9 and a recent workshop summary on this subject covers basic and clinical aspects.'j Human peripheral blood lymphocytes have proved to be rich sources of lymphokine-containing supernatants and have been used for most studies on in vitro lymphokine properties. We have used lymphoblast cell lines as sources of starting material rather than antigen or lectin-stimulated peripheral blood lymphocytes. The purpose has been solely to obtain large quantities of starting material for use in animal studies, preclinical and clinical toxicity studies, standardizing tests for biological properties, and biochemical characterization. In all of these studies, large quantities of starting materials from the same lot are required in order to compare effects on a regular basis. In spite of using the same cell line, variations in the biological properties of supernatants from lot to lot have provided some difficulties in the preparation and purification of materials, as well as biological assay. Early laboratory and clinical studies have been published and I report here our more recent mouse tumor assay experiments and some of the B-cell stimulation studies performed by Drs. Butler and Specter in Dr. Herman Friedman's laboratory.Methodology for the establishment and maintenance of human lymphoid cell lines has been described,' as well as the preparation of supernatant lympho-*

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