Eukaryotic cells respond to different extracellular stimuli by recruiting homologous signalling pathways that use members of the MEKK, MEK and ERK families of protein kinases. The MEKK-->MEK-->ERK core pathways of Saccharomyces cerevisiae may themselves be regulated by members of the STE20 family of protein kinases. Here we report specific activation of the mammalian stress-activated protein kinase (SAPK) pathway by germinal centre kinase (GCK), a human STE20 homologue. SAPKs, members of the ERK family, are activated in situ by inflammatory stimuli, including tumour-necrosis factor (TNF) and interleukin-1, and phosphorylate and probably stimulate the transactivation function of c-Jun. Although GCK is found in many tissues, its expression in lymphoid follicles is restricted to the cells of the germinal centre, where it may participate in B-cell differentiation. Activation of the SAPK pathway by GCK illustrates further the striking conservation of eukaryotic signalling mechanisms and defines the first physiological function of a mammalian Ste20.

We studied 17 patients with severe systemic necrotizing vasculitis over an 11-year-period. Sixteen patients were treated daily with cyclophosphamide (2 mg per kilogram per day), and one was treated with azathioprine (2 mg per kilogram per day). Before entering the study, all patients had active and progressive disease, even though 16 patients had been receiving corticosteroids that had caused severe and often incapacitating toxic side effects. Three patients died during the study. Complete and often dramatic remissions occurred in the surviving 14 patients, who were then placed on alternate-day corticosteroid treatment with continuation of cyclophosphamide. Corticosteroids were later discontinued in seven patients. The mean duration of remission was 22 months (range, two to 61). No patient showed recurrence of disease during treatment with cytotoxic agents.

No abstract