| |
|
|
|
|
|
|
|||
|
W Borth, A Urbanski, R Prohaska, M Susanj and TA Luger
Institute of Immunology, Medical School, University of Vienna, Australia.
Activation of human normal serum with tetanus/antitetanus immune complexes
(TAT-IC) resulted in increased binding of 125I-labeled interleukin-1 beta
(IL-1 beta) to serum factors, as opposed to untreated serum. Sodium dodecyl
sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by
autoradiography showed labeling of two large molecular mass factors of an
apparent molecular weight (Mr) of 200,000 and 400,000, respectively. These
complexes could be dissociated by reduction. No complexes were formed when
reducing compounds were added to serum-TAT-IC-125I-IL-1 beta mixtures.
Complex formation was largely prevented by alkylating compounds. Molecular
sieve chromatography of TAT-IC-activated serum confirmed that 125I-IL-1
beta became bound to high Mr serum proteins. Fractions containing high
molecular 125I-IL-1 serum protein complexes partially retained IL-1- like
activity since they induced proliferation of an IL-1-dependent murine T
helper (D10G4) cell lineage. The 125I-IL-1 beta binding factors could be
immunoprecipitated from TAT-IC-activated serum 125I-IL- 1 beta solutions by
antisera to alpha 2-macroglobulin (alpha 2M) or to the third complement
component (C3). SDS-PAGE of the immunoprecipitates showed radioactive bands
corresponding to the expected Mr resulting from complex formation between
125I-IL-1 beta and these two proteins. Treatment of purified plasma alpha
2M and C3 with trypsin or activation with methylamine, which causes
cleavage of the internal thiol ester and the appearance of free thiol
groups in these proteins, mediated binding of 125I-IL-1 beta to alpha 2M
and C3b. The results suggest that cleavage of the internal thiol ester in
C3 and alpha 2M makes these plasma proteins susceptible to binding of
125I-IL-1 beta and that free thiol groups do play a role in the formation
of 125I-IL-1 beta plasma protein complexes. Activated C3 and alpha 2M may
function as IL-1 beta carrier proteins in biologic fluids, in addition to
their other physiologic roles.
This article has been cited by other articles:
| ||||||||||
| Copyright © 1990 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||