Increased serum levels of osteoclast activating cytokines as a possible reason for osteoporosis in patients with common variable immunodeficiency (CVID)

Increased serum levels of interleukin-6 (IL-6) have repeatedly been reporte d in patients suffering form CVID, and have been blamed to contribute to th e osteoporotic process observed in these patients. In fact, IL-6 is conside red to be a major factor in osteoporosis in post-menopausal women and other conditions accompanied with loss of sex hormones. Recent investigations id entified other cytokines using the gp130 signal transducer molecule, namely oncostatin M, leukemia inhibitory factor, ciliary neurotrophic factor, and most prominently interleukin-ll (IL-11) as major osteoclast-activating fac tors. Here we show that the extremly elevated levels of IL-6 reported in ea rlier works may be caused in part by IL-11. Also, we report dramatically in creased levels of IL-11 bioactivity and protein content in the sera of pati ents with CVID. We consider this to be additional proof that cytokines acti ng through gp 130 play an essential role in osteoporosis in these patients and to warrant an investigation of other gp 130-activating cytokines in CVI D.