C567-initiated cytolysis of lymphoid cells: description of the phenomenon and studies on its control by C567 inhibitors.

Cells of the Raji human lymphoblastoid line, when pretreated with the metabolic inhibitor puromycin were found to be susceptible to killing by the isolated proteins of the complement attack mechanism (C5-9). Incubation of 51Cr-labeled lymphoblastoid cells with purified C56 and C7 resulted in the formation of a lymphoblast-C567 (LC567) intermediate, and the addition of purified human C8 and C9 resulted in release of 51Cr from these cells. Serum C567 inhibitors (C567-INH), purified human lipoproteins, and dextran sulfate, each previously shown to inhibit the attachment of the C567 trimolecular complex to erythrocytes, also inhibited the formation of LC567, and as a consequence, C56-initiated cytotoxicity; the polycation protamine sulfate counteracted the inhibitory effect of dextran sulfate. Thus, the potential for damage of bystander nucleated cells exists when C56 is generated in solution, and is influenced by agents known to modulate the hemolytic activity of C567. It is suggested that these mechanisms may be involved in the control of the function as well as the viability of various nucleated cells.