Molecular weight analysis of Fc gamma-binding proteins of lymphoid leukemia, myeloid leukemia, and hairy-cell leukemia.

The molecular weights of EDTA-mercaptoethanol-soluble Fc gamma-affined proteins isolated from chronic lymphocytic leukemia of the B type, prolymphocytic leukemia of the B type, chronic myeloid leukemia and hairy-cell leukemia were compared. SDS polyacrylamide gel electrophoresis of the Fc gamma-binding material obtained from all six cases of B type leukemia revealed a single peak with an apparent molecular weight of 28,000. The Fc gamma-affined material isolated from the cells of two cases of chronic myeloid leukemia showed two peaks, one with an apparent molecular weight of 42,600 and one with an apparent molecular weight of 18,800. The Fc gamma-affined material isolated from the cells of two cases of hairy-cell leukemia electrophoresed in the form of a closely spaced double peak. One component of the double peak had an apparent molecular weight of 28,000 and thus corresponds to the Fc gamma-binding material of leukemic B cells. The second component had a slightly lower molecular weight. The latter component is not present on either leukemic B cells or myeloid cells. The results indicate that the EDTA-mercaptoethanol-soluble Fc gamma-affined proteins of different types of cells differ in molecular weight, and thus in molecular structure.