Correlation of IL-6 with the classical humoral disease activity parametersESR and CRP and with serum cortisol, reflecting the activity of the HPA axis in active rheumatoid arthritis
B. Boss et G. Neeck, Correlation of IL-6 with the classical humoral disease activity parametersESR and CRP and with serum cortisol, reflecting the activity of the HPA axis in active rheumatoid arthritis, Z RHEUMATOL, 59, 2000, pp. 62-64
Rheumatoid arthritis (RA) is a systemic inflammatory disease with elevated
levels of proinflammatory cytokines in peripheral blood, especially IL-6, b
ut also IL-1 alpha and TNF alpha, for example, in different concentrations,
depending on disease activity. A disturbed circadian rhythm of cortisol se
cretion and an overall elevated cortisol release in active RA, depending on
disease activity, is known.
The presented study examined correlations of IL-6 as the most important sys
temic mediator of the acute phase response in active RA with classical humo
ral disease activity parameters, such as erythrocyte sedimentation rate (ES
R) and C-reactive protein (CRP), and with serum cortisol.
We investigated 64 active RA patients, previously untreated with glucocorti
coids. IL-6 was measured by ELISA from Pharmingen (San Diego), ESR by the m
ethod of Westergren and CRP by nephelometry (Behring Marburg, Germany). Cor
tisol was measured in 34 of these patients, using a fluorescence-polarizati
on immunoassay (FPIA) from Abbott.
We found correlations of IL-6 with CRP (p < 0.001, Spearman Rank Test, r(s)
= 0.75), with ESR (p < 0.001, r(s) = 0.62) and with serum cortisol(p = 0.0
19, r(s) = 0.401). ESR and CRP correlate (p < 0.001, r(s) = 0.8) and cortis
ol also correlates with ESR (p = 0.002, r(s) = 0.52) and CRP (p < 0.001, r(
s) = 0.57).
IL-6 as an important systemic mediator of inflammation in RA correlates clo
sely with CRP, as it induces its production, and with ESR. These three para
meters correlate well with serum cortisol, which is increased in active RA,
depending on disease activity.
Thus, IL-6 is an important disease activity parameter in RA that is closely
related to both the classical humoral disease activity and the HPA axis.