Cultured human lymphoblastoid cells derived from patients with Burkitt's lymphoma or infectious mononucleosis have been shown to activate the alternative complement pathway by an antibody-independent mechanism. Lymphocytes from normal or leukemic patients do not have this activity.

All lymphoblastoid cells and most lymphoma lines derived from patients with Burkitt's lymphoma carry Epstein-Barr virus DNA in their genome. Recently, EBV-negative Burkitt lymphoma lines have been established and these can be converted to EBV-positive sublines by superinfection in vitro with EBV. The existence of these lines allows us to test the hypothesis that transformation of cells with EBV confers on them the property of activating the alternative pathway.

Two EBV-negative lines and eight EBV converted sublines were tested for their ability to activate the alternative pathway in hypogammaglobulinaemic and normal human serum. Activation was assayed by demonstrating bound C3 on the membrane by immunofluorescence; by measuring C3 conversion in the serum by the Laurell technique; and consumption of total alternative pathway activity in serum by using a hemolytic assay.

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