BM cells locally produce functional factor B, factor D, and C5. (A) Zymosan-based C3b uptake assays using factor B^−/− sera plus 1:5 diluted control media (thin line) or BM cell–conditioned media (thick line), showing that BM cell–conditioned media compensated the absence of factor B. (B) Zymosan-based C3b uptake assays using factor D^−/− sera plus 1:5 diluted control media (thin line) or BM cell-conditioned media (thick line), showing that BM cell-conditioned media compensated the absence of factor D. (C) E^shA-hemolytic assays using C5-depleted sera plus 1:5 diluted control media or BM cell-conditioned media, showing that BM cell-conditioned media compensated the absence of C5, therefore inducing C5b-9 mediated hemolysis. Representative results of > 4 independent experiments.