Antigen solubilized from human leukemia: lymphocyte stimulation.

Soluble antigen was extracted with hypertonic (3 molar) potassium chloride from the malignant cells of seven patients with acute leukemia. The antigen and leukemia cells were used to stimulate autologous patients' and allogeneic normal donors' lymphocytes in mixed lymphocyte cultures. The lymphocytes of six patients showed significant blastogenic responses to autologous antigen.

Cells capable of colony formation in the peripheral blood of man.

Colony-forming cells have been found in the peripheral blood of man and have been grown in vitro by use of a soft agar gel technique. It has been possible to collect these cells with a blood-cell separator in numbers similar to those found in the peripheral circulation. Repeat leukapheresis of the same donor does not reduce the number of circulating colony-forming cells.

The human primary immune response to keyhole limpet haemocyanin: interrelationships of delayed hypersensitivity, antibody response and in vitro blast transformation.

The immune response to a protein antigen, keyhole limpet haemocyanin, was studied in fourteen normal subjects and twenty-one patients with solid tumours. Immunological responsiveness was assessed by intracutaneous skin testing, by haemagglutinin titres and by blast transformation. No significant difference was found in the kinetics or magnitude of the immune response among subjects immunized with 0·01, 0·10, or 5·0 mg.