Transfection of L929 Cells with Complement Subcomponent C1q B-Chain Antisense cDNA Inhibits Tumor Necrosis Factor-α Binding to Mediate Cytotoxicity and Nitric Oxide Generation

The role of complement subcomponent C1q in the modulation of TNF-α binding to L929 cells to mediate cytotoxicity and nitric oxide (NO) generation was investigated. Transfection of L929 with murine C1q B-chain antisense plasmid cDNA rendered them markedly less susceptible to TNF-mediated cytotoxicity coincident with a decreased capacity for TNF-α binding and expression of cell surface C1q protein. The inhibitory effects of L929 transfection with C1q B-chain antisense were transiently expressed at 24 hr post-transfection with full recovery of cellular functions by 72 hr. Transfected L929 cells were fully reconstituted in their TNF-α binding and in their cytotoxic response following exposure to soluble C1q which was bound to their cell surface. Transfection with C1q B-chain antisense also significantly inhibited NO generation by L929 cells in response to stimulation by TNF-α, IFN-α/β, and LPS. Taken together, these results indicate that endogenously synthesized C1q is prerequisite for binding of TNF-α to L929 cells to mediate cytotoxicity and NO generation.