Immunoglobulin (Ig) gene hypermutation can be induced in the BL2 Burkitt's lymphoma cell line by IgM cross-linking and coculture with normal or transformed T helper clones. We describe here a T cell#150;independent in vitro induction assay, by which hypermutation is induced in BL2 cells through simultaneous aggregation of three surface receptors: IgM, CD19 and CD21. The mutations arise as a post-transcriptional event within 90 min. They are stably introduced in the G1 phase of the cell cycle, occurring in one of the two variable gene DNA strands, and eventually become fixed by replication in one of the daughter cells. Inactivation of AID (activation-induced cytidine deaminase) by homologous recombination in BL2 cells completely inhibits the process, thus validating this induction procedure as a model for the in vivo mechanism.

Objective. To define the most effective treatment for severe polyarteritis nodosa (PAN) and ChurgStrauss syndrome (CSS) and to investigate the indication for plasma exchange treatment.Methods. We conducted a prospective, randomized, multicenter trial in which 62 patients were randomly assigned to receive either prednisone plus cyclophosphamide (intravenous bolus) (group A; n = 28) or prednisone plus cyclophosphamide (intravenous bolus) plus plasma exchanges (group B; n = 34) as first-line treatment for severe PAN or CSS. Factors predicting poor prognosis were renal symptoms, gastrointestinal tract involvement, cardiomyopathy, central nervous system involvement, weight loss >lo% of body weight, and age >SO years oid. Patients with hepatitis B virusrelated PAN were not included in this study. The end point of the study was control of the disease (recovery or remission) or death.

Objective. To define the most effective treatment for polyarteritis nodosa (PAN) and Churg‐Strauss syndrome (CSS). Methods. We conducted a prospective, randomized, multicenter trial in which 78 patients were randomly assigned to receive either prednisone and plasma exchange (group A; n = 36) or prednisone alone (group B; n = 42) as first‐line treatment of PAN and CSS. Patients with hepatitis B virus—related PAN were not included in this study. The end point of the study was control of the disease (recovery and remission) or death. Results. Clinical symptoms and laboratory findings did not differ statistically in the 2 groups at study entry. Initial control of the disease was similar in both groups. The assigned treatment was stopped in 16 patients because of lack of efficacy. Oral cyclophosphamide or dapsone therapy reversed the disease evolution in 7 of these 10 group A patients and in 4 of these 6 group B patients. At 7 years of followup, 56 patients had completely recovered (27 in group A, 29 in group B), 7 patients were in clinical remission, and 15 patients had died (19.2%; 6 group A patients and 9 group B patients). The prednisone—plasma exchange combination was no more beneficial than corticosteroids alone in preventing relapses over the long term. There was no significant difference in the 7‐year cumulative survival rates of the two groups (83% and 79%, respectively). Conclusion. Based on our data, we conclude that combined treatment with prednisone and plasma exchange is not superior to treatment with prednisone alone and must not be systematically employed for initial treatment of PAN and CSS. In most cases, cyclophosphamide as second‐line treatment is effective and well tolerated.

No abstract

No abstract