Jg. Cannon et al., MENSTRUAL-DEPENDENT AND GENDER-DEPENDENT VARIATIONS IN CIRCULATING IL-1 AGONISTS, ANTAGONISTS, AND BINDING-PROTEINS, Journal of leukocyte biology, 63(1), 1998, pp. 117-123
This study tested the hypotheses that sex-related differences in circu
lating binding proteins for interleukin-1 beta (IL-1 beta) exist and t
hat these binding proteins affect immunoassays for IL-1 beta and IL-1R
a, I-125-labeled IL-1 beta was added to human plasma samples, then chr
omatographed. The percentages of total radioactivity eluting in a high
-molecular-weight peak were 21.0 + 0.8 for men (n = 6), 19.1 +/- 0.9 f
or follicular phase women (n = 6), and 18.0 +/- 0.8 in luteal phase wo
men (n = 6; men vs, women, P = 0.032; follicular vs. luteal, P = 0.035
), and correlated with plasma sIL-1RII concentrations (r = 0.647, P =
0.001). Plasma IL-1 beta immunoreactivity did not correspond to concur
rent cellular secretion rates due, in part, to interference in the IL-
1 beta assay by sIL-1RII, Correspondence between plasma IL-1Ra levels
and cellular secretion rates was observed only after serial dilutions
of the samples, These results indicate that plasma IL-1 beta binding c
apacity differs between men and women and that sIL-1RII is a major con
tributing factor. Furthermore, relating plasma IL-1 isoform immunoreac
tivity to functional measures (tracer binding) or concurrent release b
y isolated cells can lead to insights about assay interferences that m
ay exist in plasma.