High doses of intravenous immunoglobulin do not affect the recognition
phase of the classical complement pathway
M Basta, LF Fries and MM Frank
Laboratory of Clinical Investigation, National Institute of Allergy and
Infectious Diseases, National Institutes of Health, Bethesda, MD 20982.
We have recently found that intravenous immunoglobulin (IVIg) prevents
deposition of C3 and C4 fragments onto antibody sensitized erythrocytes. To
find out if such an effect results from the blockade of the recognition
phase of the classical complement cascade, we investigated the ability of
human serum containing high concentrations of IVIg to deposit the
recognition subunit of the first complement component (C1q) onto targets.
Normal human serum supplemented in vitro with IVIg did not demonstrate
reduced C1q binding to targets as determined by radiolabeled antihuman C1q
antibody uptake. Similarly, methylamine-treated normal human serum to which
IVIg was added was equally effective in terms of C1q binding as the same
serum without IVIg. At increasing doses of sensitizing antibody, C1q uptake
decreased proportionally; however, at all antibody dilution points C1q
uptake was not significantly different in the serum with IVIg in comparison
with normal serum. Serum from a patient treated with IVIg did not differ in
its capacity to deposit C1q from the same patient's serum before therapy.
Our data suggest that IVIg does not interfere with the recognition step of
classical complement pathway. This is a US government work. There are no
restrictions on its use.
Volume 78,
Issue 3,
pp. 700-702,
08/01/1991
Copyright © 1991 by The American Society of Hematology
