DISTRIBUTION OF C3-STEP REGULATORY PROTEINS OF THE COMPLEMENT-SYSTEM,CD35 (CR-1), CD46 (MCP), AND CD55 (DAF), IN HEMATOLOGICAL MALIGNANCIES

The distribution and levels of three membrane proteins, CD35, CD46, an d CD55, which serve as complement regulators, were examined in normal peripheral blood and hematologically malignant cells. CD35 was negativ e in most leukemia cells regardless of the type of leukemia, although granulocytes, monocytes, and some populations of lymphocytes were CD35 +. CD46 was present in all blood cells except erythrocytes, and levels were 2-8 times higher in most leukemia cells than in their mature cou nterparts, particularly in CML and CLL cells, except for those of B ce ll lineage. CD55, a widely-distributed phosphatidyl inositol-anchored protein, was more frequently lost in NHL cells than in other types of hematological malignancies. In this review, we discuss the roles, mech anisms, and clinical applications of cell-associated complement regula tory proteins in hematological malignancies.