To the editor:

In their recent paper,1  Uchida and collaborators discussed the frequent presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies in pharmaceutical intravenous immunoglobulin (IVIg) preparations purified from the plasma of healthy donors, although these autoantibodies were previously reported to be rarely present in the plasma of healthy persons.2  They proposed, as an explanation for this apparent discrepancy, that GM-CSF autoantibodies were normally present in the plasma of healthy subjects at low levels and neutralized by binding to GM-CSF. This conclusion was derived from the results of experiments using low acidic pH conditions (pH 2.8) to dissociate GM-CSF from their autoreactive immunoglobulin G (IgG) followed by physical separation of the IgG and GM-CSF. This procedure was based on work by Watanabe and collaborators who used a similar protocol to show the presence of GM-CSF autoantibodies bound to GM-CSF in the plasma of healthy persons.3  The reported concentration of GM-CSF eluted from these putative immune complexes was extremely low (ie, below the sensitivity threshold of the ELISA used), yet Watanabe et al concluded that GM-CSF (approximately 10 pg/mL) was present in the eluates. This very low level of GM-CSF is much lower than the relatively high concentration of GM-CSF autoantibodies reported by Uchida et al (∼ 1 μg/mL). Such a difference does not support the hypothesis that GM-CSF autoantibodies are in a nonreactive state in the plasma of healthy persons due to the binding of their soluble antigen (GM-CSF).

Our recent work provides an alternative explanation for the presence of GM-CSF autoantibodies in IVIg preparation.4  We demonstrated that autoreactive GM-CSF antibodies were barely detectable in IgG prepared from small pools of plasma obtained from healthy persons using nondenaturing conditions (native IgG), but that treatment of native IgG under slightly denaturing conditions (pH 3.5 and 3.2) resulted in a significant increase in GM-CSF autoreactivity. In our experiments, the pH-treated native IgG preparations were neutralized without physical separation from the antigens. This would have allowed the reformation of immune complexes and the inhibition of the autoreactive IgG if GM-CSF had been present in the preparations. The pH condition (pH 2.8) used by Uchida et al is even more denaturing than those used in our study and has been known to efficiently activate cryptic autoreactive IgG.5  Therefore, we propose that autoreactive GM-CSF immunoglobulins are present in a cryptic state rather than in the form of immune complexes in the plasma of healthy persons and are detected in IVIg preparations as a consequence of modifications to the IgG structure induced by the industrial fractionation process. This conclusion could be extended to other previously described cytokine-reactive IgG observed in serum of healthy persons after low-pH exposure3  and in IVIg preparations.2,6 

Conflict-of-interest disclosure: The authors declare no competing financial interests.

Correspondence: Renée Bazin, Department of Research and Development, Héma-Québec, 1070 Ave des Sciences-de-la-Vie, Québec, QC G1V 5C3, Canada; e-mail: renee.bazin@hema-quebec.qc.ca.

1
Uchida
 
K
Nakata
 
K
Suzuki
 
T
, et al. 
Granulocyte/macrophage-colony-stimulating factor autoantibodies and myeloid cell immune functions in healthy subjects.
Blood
2009
, vol. 
113
 
11
(pg. 
2547
-
2556
)
2
Svenson
 
M
Hansen
 
MB
Ross
 
C
, et al. 
Antibody to granulocyte-macrophage colony-stimulating factor is a dominant anti-cytokine activity in human IgG preparations.
Blood
1998
, vol. 
91
 
6
(pg. 
2054
-
2061
)
3
Watanabe
 
M
Uchida
 
K
Nakagaki
 
K
, et al. 
Anti-cytokine autoantibodies are ubiquitous in healthy individuals.
FEBS Lett
2007
, vol. 
581
 
10
(pg. 
2017
-
2021
)
4
St-Amour
 
I
Laroche
 
A
Bazin
 
R
Lemieux
 
R
Activation of cryptic IgG reactive with BAFF, amyloid beta peptide and GM-CSF during the industrial fractionation of human plasma into therapeutic intravenous immunoglobulins.
Clin Immunol
2009
, vol. 
133
 
1
(pg. 
52
-
60
)
5
Bouvet
 
JP
Stahl
 
D
Rose
 
S
Quan
 
CP
Kazatchkine
 
MD
Kaveri
 
SV
Induction of natural autoantibody activity following treatment of human immunoglobulin with dissociating agents.
J Autoimmun
2001
, vol. 
16
 
2
(pg. 
163
-
172
)
6
Svenson
 
M
Hansen
 
MB
Bendtzen
 
K
Binding of cytokines to pharmaceutically prepared human immunoglobulin.
J Clin Invest
1993
, vol. 
92
 
5
(pg. 
2533
-
2539
)