Various cytokines and growth factors may be involved in IgA nephropathy. To
clarify whether interleukin-6 was a prognostic factor for this disease, we
investigated interleukin-6 positivity of renal biopsy specimens and its re
lationship with the prognosis. The subjects were 90 patients with IgA nephr
opathy (42 males and 48 females with a median age of 32.7 +/- 13.8 years).
Renal biopsy specimens were stained for interleukin-6 using an enzyme-antib
ody method. Fifty-two of 90 patients showed glomerular positivity for inter
leukin-6. Among the patients positive for interleukin-6, 24-hour urinary pr
otein excretion and serum creatinine levels were significantly higher at th
e time of biopsy than in the patients without interleukin-6 positivity, whi
le creatinine clearance was significantly lower. In the interleukin-6-posit
ive patients without steroid therapy, serum creatinine increased significan
tly after 1 year (Delta s-Cr; 1.04 +/- 0.45 mg/dl) and creatinine clearance
decreased significantly (Delta Ccr; -11.7 +/- 3.2 ml/min) compared to the
interleukin-6-negative patients without steroid therapy. Steroid therapy im
proved 24-hour urinary protein excretion, serum creatinine, and creatinine
clearance in the interleukin-6-positive patients, while these parameters wo
rsened without steroid therapy. On the other hand, the IL-6-negative patien
ts showed no differences of clinical parameters irrespective of the presenc
e or absence of steroid therapy. In conclusion, glomerular interleukin-6 po
sitivity may be a prognostic factor and an indicator of the need for steroi
d therapy in IgA nephropathy.