Human thymus-lymphoid tissue antigen and its presence in leukaemia and lymphoma.

An antiserum was prepared by immunizing rabbits with human leukaemic tissue homogenate. Prior to immunization, the rabbits had been made tolerant to normal peripheral leucocytes by repeated injections during the neonatal period to suppress the appearance of antibodies against normal tissue components. When the antiserum was tested by gel diffusion precipitation test, it gave one precipitin line against malignant tissue extracts from most leukaemia and lymphoma cases tested, and against normal thymuses and some spleens and lymph nodes as well. It did not react with tissue extracts prepared from normal non-lymphoid tissus. The antigen responsible for the reaction appeared in foetal thymus at 3 months of gestation and persisted throughout life. It appeared in embryonic spleen after 6 months of gestation and in lymph nodes even later, although in spleen and lymph nodes it was not as invariably demonstrated as in the thymus. Neoplasms of other than lymphoid origin were predominantly negative for the antigen; occasional exceptions were probably due to large amounts of infiltrating lymphoid tissue. Antigen localization was studied by the fluorescent antibody method. The cytoplasm of almost all thymocytes, about 30% spleen cells and 20–40% peripheral lymphocytes was stained. Bone marrow, brain, thyroid, liver and kidney cells were negative. The antigen was partially purified from the soluble fraction of thymus homogenate by ion exchange column chromatography and preparative electrophoresis. Its possible use as a marker for thymus derived normal and neoplastic cells has been discussed.