Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.
Inhibition of Interferon-Alpha by Sialylated IgG in Response to TLR7 and TLR9 Activation Is Mediated by a Soluble Factor Produced by Monocytes.
Wiedeman2, Alice E., Santer2, Deanna M., Kasermann1, Fabian, Miescher1, Sylvia, Elkon2, Keith B.
IgG in the form of intravenous immunoglobulin (IVIg) has been used as an anti-inflammatory agent in multiple autoimmune diseases. Recent studies reported that it is the small fraction of sialylated IgG (SA+) in human IVIg preparations that attenuates arthritis or immune thrombocytopenia. However, these studies were performed across species (human IgG injected into mouse models of disease). Our goal was to study the importance of the sialylated subset of IVIg in the inhibition of the inflammatory responses of human cells stimulated with TLR7 and 9 agonists that induce type 1 IFN.
Human IVIg preparations were enriched (SA+, 7- to 10-fold) or depleted (SA-, 2- to 5-fold) of the sialylated subset by lectin affinity chromatography. PBMC were isolated from whole blood of healthy individuals, cultured overnight in the presence of TLR7 (Loxoribine, CL097) or TLR9 (CpG) agonists with or without SA+ or SA- IgG at two doses (0.5 and 5 mg/mL). Antibodies to DC-SIGN, Fc receptors, as well as isotype controls (1ug/mL) were also used. In certain experiments, monocytes, B cells or NK cells were depleted or isolated from PBMC using magnetic beads. Some cultures were treated with TNF-a, IL-10, IL-6, and IL-8 or with antibodies to these same cytokines. Supernatants were collected 20 hours post-treatment and analyzed by ELISA for IFN-a, TNF-a, IL-10, IL-8, and IL-6.
In response to the TLR agonists tested, SA+ IgG inhibited IFN-a production significantly more than SA- IgG (p<0.05), and the inhibition by SA+ IgG increased with higher doses (p<0.05). Blocking DC-SIGN or FcRs did not abrogate the inhibition by SA+ IgG. Inhibition of IFN-a by SA+ IgG was decreased by the depletion of CD14+ monocytes, but not depletion of CD19+ B cells or CD56+ NK/NKT cells. Supernatants from isolated monocyte cultures treated with SA+ IgG could transfer inhibition to fresh cultures of TLR agonist-stimulated PBMC or isolated pDC. Surprisingly, levels of TNF-a, IL-10, IL-6, and IL-8 were not inhibited by SA+ or SA- IgG, and in fact the production of TNF-a was modestly enhanced in cultures treated with SA+ compared to SA- IgG (p<0.05). Neutralization of TNF-a or IL-10 did not abrogate IFN-a inhibition by SA+ IgG.
SA+ IgG is more potent at inhibiting IFN-a production in response to TLR agonist stimulation compared to SA- IgG. Results suggest that SA+ mediated inhibition is not mediated through an Fc gamma receptor nor the human homolog of SIGN-R1, DC-SIGN. Soluble factor(s) produced by CD14+ monocytes mediate this inhibition by acting directly on pDC. Cytokine blocking studies indicate that cytokines TNF-a and IL-10, that are produced by monocytes and known to inhibit IFN-a, are not responsible. The greater potency of SA+ IgG has therapeutic implications for SLE because our results suggest that a lower dose of IVIG enriched for the active, sialylated subset may dampen IFN-a responses to TLR stimuli. Also, identification of the SA+ binding receptor and soluble factor(s) released from monocytes in response to SA+ IgG could reveal new targets for immune modulation of type 1 IFN in SLE.
To cite this abstract, please use the following information:
Wiedeman, Alice E., Santer, Deanna M., Kasermann, Fabian, Miescher, Sylvia, Elkon, Keith B.; Inhibition of Interferon-Alpha by Sialylated IgG in Response to TLR7 and TLR9 Activation Is Mediated by a Soluble Factor Produced by Monocytes. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :494