In Vitro Lymphocyte Stimulation by a Soluble Antigen from Malignant Melanoma

Abstract

The lymphocytes of seven patients with malignant melanoma were stimulated when cultured in vitro with extracts of autologous tumor. One patient had a cystic neoplasm, which contained an electrophoretically homogeneous protein. This substance stimulated the patient's own lymphocytes in vitro, as well as those from the other six patients. Lymphocytes from normal persons did not respond to tumor extracts or to the cystictumor fluid. The mitogenic material in the tumor fluid had the electrophoretic mobility of a beta globulin and could be separated from the bulk of melanin pigments by starch-block electrophoresis. The urine of this patient also contained a homogeneous protein that was mitogenic in the presence of lymphocytes from patients with melanoma. Gel-diffusion analysis using rabbit antiserums against the tumor fluid and urinary mitogen showed that they were antigenically identical.