Serum BLyS levels correlate with transformation and response to therapy. Serum BLyS levels were analyzed by ELISA in specimens obtained from patients with NHL before (pretransformation; n = 12) and after (n = 33) transformation to DLC lymphoma (transformed) (A). (B) Serum BLyS levels were analyzed in patients with transformed DLC lymphoma (transformed; n = 33) who did (responder; n = 11) or did not (nonresponder; n = 7) respond clinically to subsequent therapy. (C) Serum BLyS levels were analyzed in newly diagnosed patients with de novo large cell lymphoma (diagnosis; n = 67) who did (responder; n = 12) or did not (nonresponder; n = 14) respond clinically to subsequent therapy (C). The results are presented as the mean ± SE.