Characterization and classification of rat leukemias and lymphomas by membrane markers.

An immunological characterization of leukemias and lymphomas was made in the rat by using a panel of membrane markers in combination with morphological analysis. In the present study, five antigen markers and three surface markers were used for the characterization of 20 rat leukemias and lymphomas, and it was indicated that they could be divided into at least six groups. Of the lymphomas studied, six thymic lymphomas (Group 1) had the Thy-1.1 antigen, T-cell antigen, and receptors for guinea pig red blood cells; five extrathymic lymphomas (Group 2) lacked T- and B-cell antigens, receptors for guinea pig red blood cells, and surface immunoglobulin, but three of them had complement receptors. An absorption test revealed that Group 2 lymphomas possess a very low amount of the Thy-1.1 antigen compared to Group 1 lymphomas. None of the leukemias studied had detectable T- and B-cell antigen. Four leukemias had undifferentiated blast cell morphology and bore the Thy-1.1 antigen; three leukemias (Group 3) reacted with anti-lymphocyte serum, but one leukemia (Group 4) did not. Two leukemias (Group 5) had only the complement receptor and morphologically showed granulocytic appearance. Three leukemias (Group 6) had none of the membrane markers used and morphologically resembled erythroblasts. Based on these results, an attempt was made to classify these leukemias and lymphomas into T-cell lineage, B-cell lineage, stem cell, myeloid, and erythroid groups, respectively. Furthermore, the stage of differentiation in the lymphocyte maturational pathway of the leukemias and lymphomas belonging to Groups 1 to 4 is discussed.