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The exposure of autoantigens by microparticles underlies the formation of potent inflammatory components: the microparticle-associated immune complexes.

Cloutier N, Tan S, Boudreau LH, Cramb C, Subbaiah R, Lahey L, Albert A, Shnayder R, Gobezie R, Nigrovic PA, Farndale RW, Robinson WH, Brisson A, Lee DM, Boilard E - EMBO Mol Med (2012)

Bottom Line: Rather, mpICs display autoantigens vimentin and fibrinogen, and recognition of these targets by anti-citrullinated peptide antibodies contributes to the production of mpICs.Functionally, platelet mpICs are highly pro-inflammatory, eliciting leukotriene production by neutrophils.Taken together, our data suggest a unique role for platelet MPs as autoantigen-expressing elements capable of perpetuating formation of inflammatory ICs.

View Article: PubMed Central - PubMed

Affiliation: Faculté de Médecine de l'Université Laval, Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec, Canada.

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Platelet MPs display citrullinated autoantigens recognized by IgG from RA SFA,B The presence of citrullinated epitopes on platelet MPs was determined by hs-FCM using anti-citrulline antibody and its corresponding secondary antibody conjugated to Alexa 647. MPs were confirmed of platelet origin using a PE-conjugated anti-CD41 antibody. (A) The presence of citrullinated antigens on platelet MPs was determined in in vitro platelet MPs (left panel) and MPs from RA SF (right panel). The vertical lines were positioned according to the isotypic controls. Pink: Negative population; blue: Positive population. The % of positive platelet MPs is indicated on graphs. (B) Quantification of the citrulline+ CD41+ MPs in RA and PA SF (n = 8 RA and n = 8 PA *p = 0.0148).C,D The proteins from platelet MPs obtained in vitro left unmodified (−PAD4) or citrullinated (+PAD4) were separated on SDS–PAGE and transferred to membranes. The membranes were incubated in presence of RA (C) or PA (D) SF and the recognition of MP-derived autoantigens by autoantibodies from SF was revealed using HRP-conjugated anti-human IgG. Arrows indicate proteins recognized by IgG from SF uniquely when the MPs were citrullinated. Two RA and PA SF are presented to illustrate the existing variability between patients (n = 12 RA and n = 8 PA).
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fig05: Platelet MPs display citrullinated autoantigens recognized by IgG from RA SFA,B The presence of citrullinated epitopes on platelet MPs was determined by hs-FCM using anti-citrulline antibody and its corresponding secondary antibody conjugated to Alexa 647. MPs were confirmed of platelet origin using a PE-conjugated anti-CD41 antibody. (A) The presence of citrullinated antigens on platelet MPs was determined in in vitro platelet MPs (left panel) and MPs from RA SF (right panel). The vertical lines were positioned according to the isotypic controls. Pink: Negative population; blue: Positive population. The % of positive platelet MPs is indicated on graphs. (B) Quantification of the citrulline+ CD41+ MPs in RA and PA SF (n = 8 RA and n = 8 PA *p = 0.0148).C,D The proteins from platelet MPs obtained in vitro left unmodified (−PAD4) or citrullinated (+PAD4) were separated on SDS–PAGE and transferred to membranes. The membranes were incubated in presence of RA (C) or PA (D) SF and the recognition of MP-derived autoantigens by autoantibodies from SF was revealed using HRP-conjugated anti-human IgG. Arrows indicate proteins recognized by IgG from SF uniquely when the MPs were citrullinated. Two RA and PA SF are presented to illustrate the existing variability between patients (n = 12 RA and n = 8 PA).

Mentions: Autoantibody/antigen binding comprises another plausible mechanism for formation of mpIC. Among the mechanisms that occur in RA SF and not in PA SF is citrullination, a process that generates neoepitopes recognized by autoantibodies present in abundance in many patients with RA (Yoshida et al, 2006). Specifically, citrullination is a posttranslational modification of peptidyl-arginine to peptidyl-citrulline by peptidyl arginine deiminase (PAD) enzymes; in RA SF, the PAD4 isoform levels are significantly elevated (Arita et al, 2004; Lundberg et al, 2005). Given that MPs are present in a milieu where citrullination is active, we hypothesized that the MP surface proteins may become citrullinated and give rise to autoantigens recognized by autoantibodies in RA patients and thereby promote mpIC formation. Using hs-FCM, we first evaluated whether platelet MPs are citrullinated in the course of RA pathogenesis. We find that, unlike platelet MPs generated in vitro and those in PA SF, the platelet MPs in RA SF contain citrullinated epitopes (Fig 5A and B), pointing to citrullination of MPs as a potential mechanism leading to recognition by autoantibodies.


The exposure of autoantigens by microparticles underlies the formation of potent inflammatory components: the microparticle-associated immune complexes.

Cloutier N, Tan S, Boudreau LH, Cramb C, Subbaiah R, Lahey L, Albert A, Shnayder R, Gobezie R, Nigrovic PA, Farndale RW, Robinson WH, Brisson A, Lee DM, Boilard E - EMBO Mol Med (2012)

Platelet MPs display citrullinated autoantigens recognized by IgG from RA SFA,B The presence of citrullinated epitopes on platelet MPs was determined by hs-FCM using anti-citrulline antibody and its corresponding secondary antibody conjugated to Alexa 647. MPs were confirmed of platelet origin using a PE-conjugated anti-CD41 antibody. (A) The presence of citrullinated antigens on platelet MPs was determined in in vitro platelet MPs (left panel) and MPs from RA SF (right panel). The vertical lines were positioned according to the isotypic controls. Pink: Negative population; blue: Positive population. The % of positive platelet MPs is indicated on graphs. (B) Quantification of the citrulline+ CD41+ MPs in RA and PA SF (n = 8 RA and n = 8 PA *p = 0.0148).C,D The proteins from platelet MPs obtained in vitro left unmodified (−PAD4) or citrullinated (+PAD4) were separated on SDS–PAGE and transferred to membranes. The membranes were incubated in presence of RA (C) or PA (D) SF and the recognition of MP-derived autoantigens by autoantibodies from SF was revealed using HRP-conjugated anti-human IgG. Arrows indicate proteins recognized by IgG from SF uniquely when the MPs were citrullinated. Two RA and PA SF are presented to illustrate the existing variability between patients (n = 12 RA and n = 8 PA).
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Related In: Results  -  Collection

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fig05: Platelet MPs display citrullinated autoantigens recognized by IgG from RA SFA,B The presence of citrullinated epitopes on platelet MPs was determined by hs-FCM using anti-citrulline antibody and its corresponding secondary antibody conjugated to Alexa 647. MPs were confirmed of platelet origin using a PE-conjugated anti-CD41 antibody. (A) The presence of citrullinated antigens on platelet MPs was determined in in vitro platelet MPs (left panel) and MPs from RA SF (right panel). The vertical lines were positioned according to the isotypic controls. Pink: Negative population; blue: Positive population. The % of positive platelet MPs is indicated on graphs. (B) Quantification of the citrulline+ CD41+ MPs in RA and PA SF (n = 8 RA and n = 8 PA *p = 0.0148).C,D The proteins from platelet MPs obtained in vitro left unmodified (−PAD4) or citrullinated (+PAD4) were separated on SDS–PAGE and transferred to membranes. The membranes were incubated in presence of RA (C) or PA (D) SF and the recognition of MP-derived autoantigens by autoantibodies from SF was revealed using HRP-conjugated anti-human IgG. Arrows indicate proteins recognized by IgG from SF uniquely when the MPs were citrullinated. Two RA and PA SF are presented to illustrate the existing variability between patients (n = 12 RA and n = 8 PA).
Mentions: Autoantibody/antigen binding comprises another plausible mechanism for formation of mpIC. Among the mechanisms that occur in RA SF and not in PA SF is citrullination, a process that generates neoepitopes recognized by autoantibodies present in abundance in many patients with RA (Yoshida et al, 2006). Specifically, citrullination is a posttranslational modification of peptidyl-arginine to peptidyl-citrulline by peptidyl arginine deiminase (PAD) enzymes; in RA SF, the PAD4 isoform levels are significantly elevated (Arita et al, 2004; Lundberg et al, 2005). Given that MPs are present in a milieu where citrullination is active, we hypothesized that the MP surface proteins may become citrullinated and give rise to autoantigens recognized by autoantibodies in RA patients and thereby promote mpIC formation. Using hs-FCM, we first evaluated whether platelet MPs are citrullinated in the course of RA pathogenesis. We find that, unlike platelet MPs generated in vitro and those in PA SF, the platelet MPs in RA SF contain citrullinated epitopes (Fig 5A and B), pointing to citrullination of MPs as a potential mechanism leading to recognition by autoantibodies.

Bottom Line: Rather, mpICs display autoantigens vimentin and fibrinogen, and recognition of these targets by anti-citrullinated peptide antibodies contributes to the production of mpICs.Functionally, platelet mpICs are highly pro-inflammatory, eliciting leukotriene production by neutrophils.Taken together, our data suggest a unique role for platelet MPs as autoantigen-expressing elements capable of perpetuating formation of inflammatory ICs.

View Article: PubMed Central - PubMed

Affiliation: Faculté de Médecine de l'Université Laval, Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec, Canada.

Show MeSH
Related in: MedlinePlus