The use of radioisotopes for cell labeling has been a major tool in hematology laboratory research. Chromium-51-labeling of hematologic cells and lymphocytes has been used for years to study the migration and sequestration of these cells in the spleen and other sites. The substantial recirculation of lymphocytes from blood into lymphoid tissue and back into blood is well described. Recently, new approaches for radiosotopic cell labeling have gained prominence in the investigation of various aspects of malignant diseases and in the clinical care of such patients. Isotopes such as indium-111 can be visualized with standard scanning techniques providing further information about the migration of normal and malignant cells has been discovered.
In vivo studies have been performed with indium-111 in animals and humans, including comparisons of the migration of abnormal cells (malignant) and of lymphocytes to abnormal nodes. Evaluation and comparison of the migration of carcinoma cells, normal lymphoid cells, and malignant lymphoid cells in animals show markedly different patterns of distribution, which could have bearing on investigations of mechanisms of metastasis. In vivo human studies also have evaluated the migration patterns of lymphoid cells from patients with chronic lymphocytic leukemia and well-differentiated lymphoma, showing very different migrating behavior between these two polarities of a similar disease. These types of studies, while initially phenomenonologic, may provide a basis for a better understanding of these diseases.
There are concerns about the use of an isotope such as indium-111 for the labeling of long-lived cells such as lymphocytes. Laboratory studies have demonstrated impaired cell function at high concentrations of radioactivity. Some workers have expressed concern about long-term changes in cells that recirculate. Others cite precedents of other long-term uses of isotopes, therapeutically, without detrimental effects. These concerns continue to be investigated.
Finally, an area of much interest in the use of indium-111 is the labeling of granulocytes. This technique has been useful diagnostically, to localize infections. The major value in patients with malignancy, primarily with hematologic malignancies, is to evaluate the potential benefit of granulocyte transfusions. Many of these patients develop prolonged granulocytopenia and become infected, and granulocyte transfusions may become a therapeutic consideration. However, these patients usually have been subjected to many transfusions and may be immunized to granulocytes. This is difficult to assess clinically, but the use of indium-111-labeled donor granulocytes provides a visual demonstration of whether or not the cells migrate to the site of infection. This technique also can be used to assess granulocyte sequestration. It appears that in patients who develop antibodies, both anti-HLA and granulocyte specific, the donor granulocytes do not migrate to sites of infection and in fact may sequester in the lungs. These data can help guide the use of granulocyte transfusion in these patients.
The investigation of labeled cells, both malignant and normal, in patients with malignancy is giving us new insight into the diseases. These studies are of particular benefit using newer techniques with isotopes that can be scanned such as indium-111. Studies of the migration patterns of Sezary cells, granulocytes in chronic myelogenous leukemia and lymphocytes in lymphoid leukemia are continuing and may provide important information regarding the disease process.
