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Modulation of immune complex-induced inflammation in vivo by the coordinate expression of activation and inhibitory Fc receptors.

Clynes R, Maizes JS, Guinamard R, Ono M, Takai T, Ravetch JV - J. Exp. Med. (1999)

Bottom Line: An inhibitory role for FcgammaRII on macrophages is demonstrated by analysis of FcgammaRII-/- macrophages which show greater phagocytic and calcium flux responses upon FcgammaRIII engagement.These data reveal contrasting roles for the cellular receptors for IgG on inflammatory cells, providing a regulatory mechanism for setting thresholds for IC sensitivity based on the ratio of ITIM to ITAM FcgammaR expression.Exploiting the FcgammaRII inhibitory pathway could thus provide a new therapeutic approach for modulating antibody-triggered inflammation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Genetics and Immunology, The Rockefeller University, New York 10021, USA.

ABSTRACT
Autoantibodies and immune complexes are major pathogenic factors in autoimmune injury, responsible for initiation of the inflammatory cascade and its resulting tissue damage. This activation results from the interaction of immunoglobulin (Ig)G Fc receptors containing an activation motif (ITAM) with immune complexes (ICs) and cytotoxic autoantibodies which initiates and propagates an inflammatory response. In vitro, this pathway can be interrupted by coligation to FcgammaRIIB, an IgG Fc receptor containing an inhibitory motif (ITIM). In this report, we describe the in vivo consequences of FcgammaRII deficiency in the inflammatory response using a mouse model of IC alveolitis. At subthreshold concentrations of ICs that fail to elicit inflammatory responses in wild-type mice, FcgammaRII-deficient mice developed robust inflammatory responses characterized by increased hemorrhage, edema, and neutrophil infiltration. Bronchoalveolar fluids from FcgammaRII-/- stimulated mice contain higher levels of tumor necrosis factor and chemotactic activity, suggesting that FcgammaRII deficiency lowers the threshold of IC stimulation of resident cells such as the alveolar macrophage. In contrast, complement- and complement receptor-deficient mice develop normal inflammatory responses to suprathreshold levels of ICs, while FcRgamma-/- mice are completely protected from inflammatory injury. An inhibitory role for FcgammaRII on macrophages is demonstrated by analysis of FcgammaRII-/- macrophages which show greater phagocytic and calcium flux responses upon FcgammaRIII engagement. These data reveal contrasting roles for the cellular receptors for IgG on inflammatory cells, providing a regulatory mechanism for setting thresholds for IC sensitivity based on the ratio of ITIM to ITAM FcgammaR expression. Exploiting the FcgammaRII inhibitory pathway could thus provide a new therapeutic approach for modulating antibody-triggered inflammation.

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IC alveolitis: quantitative assessment of edema, neutrophilic infiltration, and hemorrhage in wild-type (WT), γ−/−,  C3−/−, and C5aR−/− mice. (Top)  Vasopermeability index, as assessed by Evan's blue dye extravasation into the bronchoalveolar space. (Middle) Neutrophilic  infiltration, as assessed by neutrophil-specific MPO assay. MPO  activity in lung lysates was measured at OD450. (Bottom) Alveolar  hemorrhage, as measured by total  RBC counts of BAL. Mice received OVA (IC, black bars) or  PBS (Ab, white bars) intravenously, followed by 300 μg  anti-OVA intratracheally. Experimental groups included three to  seven mice per group. PBS controls were not performed for all  genotypes. Data are presented as  mean ± SEM. The P values  for edematous, neutrophilic, and  hemorrhagic responses were as  follows: 0.02, 0.01, and 0.03, γ−/−  vs. wild-type; 0.03, 0.08, and  0.05, C3−/− vs. wild-type; and  0.08, 0.45, and 0.09, C5aR−/−  vs. wild-type, respectively. Statistical analysis was performed with  an unpaired two-tailed Student's  t test.
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Figure 2: IC alveolitis: quantitative assessment of edema, neutrophilic infiltration, and hemorrhage in wild-type (WT), γ−/−, C3−/−, and C5aR−/− mice. (Top) Vasopermeability index, as assessed by Evan's blue dye extravasation into the bronchoalveolar space. (Middle) Neutrophilic infiltration, as assessed by neutrophil-specific MPO assay. MPO activity in lung lysates was measured at OD450. (Bottom) Alveolar hemorrhage, as measured by total RBC counts of BAL. Mice received OVA (IC, black bars) or PBS (Ab, white bars) intravenously, followed by 300 μg anti-OVA intratracheally. Experimental groups included three to seven mice per group. PBS controls were not performed for all genotypes. Data are presented as mean ± SEM. The P values for edematous, neutrophilic, and hemorrhagic responses were as follows: 0.02, 0.01, and 0.03, γ−/− vs. wild-type; 0.03, 0.08, and 0.05, C3−/− vs. wild-type; and 0.08, 0.45, and 0.09, C5aR−/− vs. wild-type, respectively. Statistical analysis was performed with an unpaired two-tailed Student's t test.

Mentions: Previous studies on the FcR dependence and complement independence of IC-triggered inflammation were based on studies using models involving the skin and kidney (3–5, 36, 37). It has been suggested that IC-induced inflammation in the lung may display a greater dependence on complement activation pathways than other anatomic sites (32, 38). To delineate the relative contributions of complement- and FcR-triggered activation pathways in IC alveolitis, the inflammatory reactions of wild-type, C3- deficient, and C5aR-deficient mice were compared. Mice were killed 4 h after challenge, and lungs were processed for either histological or quantitative assessment of inflammation. Quantitative analysis included RBC counts of BAL fluid for an index of hemorrhage; measurement of Evan's blue dye extravasation into bronchoalveolar fluid for edema evaluation; and MPO assay of whole lung tissue as an indicator of neutrophil infiltration. Wild-type, C3−/−, C5aR−/−, and FcR γ−/− mice challenged with 300 μg rabbit anti-OVA IgG alone had little or no inflammatory reaction observable histologically or by quantitative assessment of hemorrhage, edema, or neutrophil infiltration (see Fig. 2, and data not shown). Wild-type mice treated with both intravenous OVA and 300 μg of anti-OVA to induce in situ formation of ICs developed robust inflammatory responses characterized by alveolar hemorrhage, neutrophil infiltration, and perivascular edema (Figs. 1 and 2). Contrary to the conclusion of a prior report that C5aR deficiency significantly attenuated inflammation in this model (32, 38), we observed minimally reduced inflammatory responses in IC-treated complement-deficient animals both qualitatively and quantitatively (Figs. 1 and 2). Histological analysis revealed that complement-deficient mice exhibited minimally attenuated hemorrhage with somewhat fewer RBCs and PMNs seen in BAL specimens (Fig. 1). Quantitative assessment revealed lowered edematous responses, but no statistically significant differences in BAL RBC counts or total lung MPO activity were detectable between wild-type and complement-deficient animals (Fig. 2). In contrast to the lack of protection in C3- and C5aR-deficient mice, protection in FcR γ−/− mice was complete. Alveolar hemorrhage is easily seen in wild-type, C3−/−, and C5aR−/− mice but not in γ−/− mice (Fig. 1 A, top panels). BAL fluids (Fig. 1, bottom panels) reveal that the airways of wild-type, C3−/−, and C5aR−/− mice are filled with RBCs and recruited neutrophils, but that the airways of γ−/− mice show little signs of inflammation and BAL specimens contain resident alveolar macrophages and few RBCs and few neutrophils. These data demonstrate that IC-triggered inflammation in the lung is FcR dependent, as has been observed in the skin and kidney, and establish the general importance of the FcR γ activation pathway, as opposed to complement, in IC injury regardless of tissue site.


Modulation of immune complex-induced inflammation in vivo by the coordinate expression of activation and inhibitory Fc receptors.

Clynes R, Maizes JS, Guinamard R, Ono M, Takai T, Ravetch JV - J. Exp. Med. (1999)

IC alveolitis: quantitative assessment of edema, neutrophilic infiltration, and hemorrhage in wild-type (WT), γ−/−,  C3−/−, and C5aR−/− mice. (Top)  Vasopermeability index, as assessed by Evan's blue dye extravasation into the bronchoalveolar space. (Middle) Neutrophilic  infiltration, as assessed by neutrophil-specific MPO assay. MPO  activity in lung lysates was measured at OD450. (Bottom) Alveolar  hemorrhage, as measured by total  RBC counts of BAL. Mice received OVA (IC, black bars) or  PBS (Ab, white bars) intravenously, followed by 300 μg  anti-OVA intratracheally. Experimental groups included three to  seven mice per group. PBS controls were not performed for all  genotypes. Data are presented as  mean ± SEM. The P values  for edematous, neutrophilic, and  hemorrhagic responses were as  follows: 0.02, 0.01, and 0.03, γ−/−  vs. wild-type; 0.03, 0.08, and  0.05, C3−/− vs. wild-type; and  0.08, 0.45, and 0.09, C5aR−/−  vs. wild-type, respectively. Statistical analysis was performed with  an unpaired two-tailed Student's  t test.
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Related In: Results  -  Collection

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Figure 2: IC alveolitis: quantitative assessment of edema, neutrophilic infiltration, and hemorrhage in wild-type (WT), γ−/−, C3−/−, and C5aR−/− mice. (Top) Vasopermeability index, as assessed by Evan's blue dye extravasation into the bronchoalveolar space. (Middle) Neutrophilic infiltration, as assessed by neutrophil-specific MPO assay. MPO activity in lung lysates was measured at OD450. (Bottom) Alveolar hemorrhage, as measured by total RBC counts of BAL. Mice received OVA (IC, black bars) or PBS (Ab, white bars) intravenously, followed by 300 μg anti-OVA intratracheally. Experimental groups included three to seven mice per group. PBS controls were not performed for all genotypes. Data are presented as mean ± SEM. The P values for edematous, neutrophilic, and hemorrhagic responses were as follows: 0.02, 0.01, and 0.03, γ−/− vs. wild-type; 0.03, 0.08, and 0.05, C3−/− vs. wild-type; and 0.08, 0.45, and 0.09, C5aR−/− vs. wild-type, respectively. Statistical analysis was performed with an unpaired two-tailed Student's t test.
Mentions: Previous studies on the FcR dependence and complement independence of IC-triggered inflammation were based on studies using models involving the skin and kidney (3–5, 36, 37). It has been suggested that IC-induced inflammation in the lung may display a greater dependence on complement activation pathways than other anatomic sites (32, 38). To delineate the relative contributions of complement- and FcR-triggered activation pathways in IC alveolitis, the inflammatory reactions of wild-type, C3- deficient, and C5aR-deficient mice were compared. Mice were killed 4 h after challenge, and lungs were processed for either histological or quantitative assessment of inflammation. Quantitative analysis included RBC counts of BAL fluid for an index of hemorrhage; measurement of Evan's blue dye extravasation into bronchoalveolar fluid for edema evaluation; and MPO assay of whole lung tissue as an indicator of neutrophil infiltration. Wild-type, C3−/−, C5aR−/−, and FcR γ−/− mice challenged with 300 μg rabbit anti-OVA IgG alone had little or no inflammatory reaction observable histologically or by quantitative assessment of hemorrhage, edema, or neutrophil infiltration (see Fig. 2, and data not shown). Wild-type mice treated with both intravenous OVA and 300 μg of anti-OVA to induce in situ formation of ICs developed robust inflammatory responses characterized by alveolar hemorrhage, neutrophil infiltration, and perivascular edema (Figs. 1 and 2). Contrary to the conclusion of a prior report that C5aR deficiency significantly attenuated inflammation in this model (32, 38), we observed minimally reduced inflammatory responses in IC-treated complement-deficient animals both qualitatively and quantitatively (Figs. 1 and 2). Histological analysis revealed that complement-deficient mice exhibited minimally attenuated hemorrhage with somewhat fewer RBCs and PMNs seen in BAL specimens (Fig. 1). Quantitative assessment revealed lowered edematous responses, but no statistically significant differences in BAL RBC counts or total lung MPO activity were detectable between wild-type and complement-deficient animals (Fig. 2). In contrast to the lack of protection in C3- and C5aR-deficient mice, protection in FcR γ−/− mice was complete. Alveolar hemorrhage is easily seen in wild-type, C3−/−, and C5aR−/− mice but not in γ−/− mice (Fig. 1 A, top panels). BAL fluids (Fig. 1, bottom panels) reveal that the airways of wild-type, C3−/−, and C5aR−/− mice are filled with RBCs and recruited neutrophils, but that the airways of γ−/− mice show little signs of inflammation and BAL specimens contain resident alveolar macrophages and few RBCs and few neutrophils. These data demonstrate that IC-triggered inflammation in the lung is FcR dependent, as has been observed in the skin and kidney, and establish the general importance of the FcR γ activation pathway, as opposed to complement, in IC injury regardless of tissue site.

Bottom Line: An inhibitory role for FcgammaRII on macrophages is demonstrated by analysis of FcgammaRII-/- macrophages which show greater phagocytic and calcium flux responses upon FcgammaRIII engagement.These data reveal contrasting roles for the cellular receptors for IgG on inflammatory cells, providing a regulatory mechanism for setting thresholds for IC sensitivity based on the ratio of ITIM to ITAM FcgammaR expression.Exploiting the FcgammaRII inhibitory pathway could thus provide a new therapeutic approach for modulating antibody-triggered inflammation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Genetics and Immunology, The Rockefeller University, New York 10021, USA.

ABSTRACT
Autoantibodies and immune complexes are major pathogenic factors in autoimmune injury, responsible for initiation of the inflammatory cascade and its resulting tissue damage. This activation results from the interaction of immunoglobulin (Ig)G Fc receptors containing an activation motif (ITAM) with immune complexes (ICs) and cytotoxic autoantibodies which initiates and propagates an inflammatory response. In vitro, this pathway can be interrupted by coligation to FcgammaRIIB, an IgG Fc receptor containing an inhibitory motif (ITIM). In this report, we describe the in vivo consequences of FcgammaRII deficiency in the inflammatory response using a mouse model of IC alveolitis. At subthreshold concentrations of ICs that fail to elicit inflammatory responses in wild-type mice, FcgammaRII-deficient mice developed robust inflammatory responses characterized by increased hemorrhage, edema, and neutrophil infiltration. Bronchoalveolar fluids from FcgammaRII-/- stimulated mice contain higher levels of tumor necrosis factor and chemotactic activity, suggesting that FcgammaRII deficiency lowers the threshold of IC stimulation of resident cells such as the alveolar macrophage. In contrast, complement- and complement receptor-deficient mice develop normal inflammatory responses to suprathreshold levels of ICs, while FcRgamma-/- mice are completely protected from inflammatory injury. An inhibitory role for FcgammaRII on macrophages is demonstrated by analysis of FcgammaRII-/- macrophages which show greater phagocytic and calcium flux responses upon FcgammaRIII engagement. These data reveal contrasting roles for the cellular receptors for IgG on inflammatory cells, providing a regulatory mechanism for setting thresholds for IC sensitivity based on the ratio of ITIM to ITAM FcgammaR expression. Exploiting the FcgammaRII inhibitory pathway could thus provide a new therapeutic approach for modulating antibody-triggered inflammation.

Show MeSH
Related in: MedlinePlus