Specific radioimmunoassays for IL 1 alpha and IL 1 beta in plasma at physiological and acidic pH: determination of immunoreactive forms by gel filtration and radioligand binding studies.
We have developed specific radioimmunoassays for interleukin 1 alpha (IL 1 alpha) and interleukin 1 beta (IL 1 beta) and applied these successfully to the measurement of interleukin 1 (IL 1) in neat plasma. Further characterization of the plasma immunoreactive forms of IL 1 was done using Sephadex G-75 chromatography and TSKG2000 high performance gel permeation chromatography. This revealed the immunoreactivity to be associated with a high molecular weight fraction for both IL 1 alpha and IL 1 beta. Incubation of plasma with iodinated IL 1 alpha and beta showed that there was a time-dependent association of tracer with the high molecular weight fraction and that this was predominantly with IL 1 beta. The activity was displaceable with unlabeled IL 1 beta, which together with the chromatography results, suggested that IL 1 beta is protein-bound in plasma. Furthermore, we have shown that under acid conditions both tracer and endogenous IL 1 beta immunoreactivity migrate as a low (17 kD) molecular weight fraction. This suggests that dissociation from a high molecular weight binder has occurred. Acid treatment of plasma raised the immunoreactive IL 1 beta level, but had no effect on IL 1 alpha levels, confirming the specificity of a binder to IL 1 beta, as shown by the tracer experiments. These results suggest that plasma contains high molecular weight binders of IL 1, particularly IL 1 beta, and that these may play a role in regulating the distribution, clearance and bioactivity of circulating IL 1.
Capper
S J
SJ
Life Sciences Business, Cardiff, Wales, U.K.
Kalinka
S
S
Mander
T H
TH
D002850:Chromatography, Gel; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007375:Interleukin-1 / Q000097:blood* / Q000737:chemistry; D008970:Molecular Weight; D011863:Radioimmunoassay
D007375:Interleukin-1