Inactivation of the IL-6 gene prevents development of multicentric Castleman's disease in C/EBPβ-deficient mice

Castleman's disease is a lymphoproliferative disorder thought to be related to deregulated production of IL-6. We have previously shown that mice lacking the trans-acting factor C/EBPβ, a transcriptional regulator of IL-6 and a mediator of IL-6 intracellular signaling, develop a pathology nearly identical to multicenter Castleman's disease, together with increasingly high levels of circulating IL-6. We described here how the simultaneous inactivation of both (IL-6 and C/EBPβ genes prevents the development of pathological traits of Castleman's disease observed in C/EBPβ-deficient mice. Histological and phenotypic analysis of lymph nodes and spleen of double mutant mice did not show either the lymphoadenopathy and splenomegaly of the abnormal expansion of myeloid, B and plasma cell compartments observed in C/EBPβ-/- mice, while B cell development, although delayed, was normal. Our data demonstrate that IL-6 is essential for the development of multicentric Castleman's disease in C/EBPβ-/- mice.