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Abrogation of immune complex glomerulonephritis by native carboxypeptidase and pharmacological antagonism of the C5a receptor

View Article: PubMed Central - PubMed

ABSTRACT

Activation of complement generates C5a which leads to signaling through C5aR1. This is tightly controlled, including by the plasma proteins factor H (FH) and carboxypeptidase N. Here we studied a chronic serum sickness (CSS) model of glomerulonephritis (GN) in which there is an active humoral immune response, formation of glomerular immune complexes (ICs), and resulting glomerular inflammation. The antibody response, glomerular IC deposition, the degree of GN, and consequent renal functional insufficiency in CSS were all worse in FH−/− mice compared to wild-type FH+/+ animals. This was ameliorated in the former by giving a C5aR1 antagonist for the final 3 weeks of the 5-week protocol. In contrast, blocking CP-mediated inactivation of C5a increased these disease measures. Thus, complement regulation by both plasma FH and CP to limit the quantity of active C5a is important in conditions where the humoral immune response is directed to a continuously present foreign antigen. Signaling through C5aR1 enhances the humoral immune response as well as the inflammatory response to ICs that have formed in glomeruli. Both effects are relevant even after disease has begun. Thus, pharmacological targeting of C5a in IC-mediated GN has potential clinical relevance.

No MeSH data available.


C5a enhances glomerular IC deposition in FH−/− mice with CSS. Representative glomerular immunofluorescence staining for C3 (green) and IgG (red) is shown for control FH−/− mice without CSS (A), FH−/− mice with CSS (B), and FH−/− mice with CSS receiving C5aRant (C) or CPinh (D). Linear glomerular capillary wall C3 staining typical for unmanipulated FH−/− mice was present in all groups. Mesangial IgG was present in all groups with CSS (white asterisks) with some extension to the peripheral capillary walls (white arrows), but in relatively lesser amounts in FH−/− mice treated with C5aRant (C) and greater amounts in those given CPinh (D), in which there was significant extension to peripheral capillary walls (double white arrows). For purposes of localization, nuclei were stained with DAPI (blue) in D. Original magnifications, ×400.
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fig5: C5a enhances glomerular IC deposition in FH−/− mice with CSS. Representative glomerular immunofluorescence staining for C3 (green) and IgG (red) is shown for control FH−/− mice without CSS (A), FH−/− mice with CSS (B), and FH−/− mice with CSS receiving C5aRant (C) or CPinh (D). Linear glomerular capillary wall C3 staining typical for unmanipulated FH−/− mice was present in all groups. Mesangial IgG was present in all groups with CSS (white asterisks) with some extension to the peripheral capillary walls (white arrows), but in relatively lesser amounts in FH−/− mice treated with C5aRant (C) and greater amounts in those given CPinh (D), in which there was significant extension to peripheral capillary walls (double white arrows). For purposes of localization, nuclei were stained with DAPI (blue) in D. Original magnifications, ×400.

Mentions: Double-label immunofluorescence microscopy was performed to evaluate glomerular IgG and C3 (Figure 5). As shown by the red staining in Figure 5B, FH−/− mice with CSS had IgG within mesangial regions (asterisks) with some extension to peripheral capillary walls (arrows). This was reduced in FH−/− mice with CSS given C5aRant (Figure 5C), and worsened in mice given CPinh (Figure 5D). As anticipated, glomeruli from FH−/− mice had linear glomerular capillary wall staining for C3; this was not appreciably affected by induction of CSS or either of the inhibitors (stained green in Figure 5).


Abrogation of immune complex glomerulonephritis by native carboxypeptidase and pharmacological antagonism of the C5a receptor
C5a enhances glomerular IC deposition in FH−/− mice with CSS. Representative glomerular immunofluorescence staining for C3 (green) and IgG (red) is shown for control FH−/− mice without CSS (A), FH−/− mice with CSS (B), and FH−/− mice with CSS receiving C5aRant (C) or CPinh (D). Linear glomerular capillary wall C3 staining typical for unmanipulated FH−/− mice was present in all groups. Mesangial IgG was present in all groups with CSS (white asterisks) with some extension to the peripheral capillary walls (white arrows), but in relatively lesser amounts in FH−/− mice treated with C5aRant (C) and greater amounts in those given CPinh (D), in which there was significant extension to peripheral capillary walls (double white arrows). For purposes of localization, nuclei were stained with DAPI (blue) in D. Original magnifications, ×400.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037280&req=5

fig5: C5a enhances glomerular IC deposition in FH−/− mice with CSS. Representative glomerular immunofluorescence staining for C3 (green) and IgG (red) is shown for control FH−/− mice without CSS (A), FH−/− mice with CSS (B), and FH−/− mice with CSS receiving C5aRant (C) or CPinh (D). Linear glomerular capillary wall C3 staining typical for unmanipulated FH−/− mice was present in all groups. Mesangial IgG was present in all groups with CSS (white asterisks) with some extension to the peripheral capillary walls (white arrows), but in relatively lesser amounts in FH−/− mice treated with C5aRant (C) and greater amounts in those given CPinh (D), in which there was significant extension to peripheral capillary walls (double white arrows). For purposes of localization, nuclei were stained with DAPI (blue) in D. Original magnifications, ×400.
Mentions: Double-label immunofluorescence microscopy was performed to evaluate glomerular IgG and C3 (Figure 5). As shown by the red staining in Figure 5B, FH−/− mice with CSS had IgG within mesangial regions (asterisks) with some extension to peripheral capillary walls (arrows). This was reduced in FH−/− mice with CSS given C5aRant (Figure 5C), and worsened in mice given CPinh (Figure 5D). As anticipated, glomeruli from FH−/− mice had linear glomerular capillary wall staining for C3; this was not appreciably affected by induction of CSS or either of the inhibitors (stained green in Figure 5).

View Article: PubMed Central - PubMed

ABSTRACT

Activation of complement generates C5a which leads to signaling through C5aR1. This is tightly controlled, including by the plasma proteins factor H (FH) and carboxypeptidase N. Here we studied a chronic serum sickness (CSS) model of glomerulonephritis (GN) in which there is an active humoral immune response, formation of glomerular immune complexes (ICs), and resulting glomerular inflammation. The antibody response, glomerular IC deposition, the degree of GN, and consequent renal functional insufficiency in CSS were all worse in FH−/− mice compared to wild-type FH+/+ animals. This was ameliorated in the former by giving a C5aR1 antagonist for the final 3 weeks of the 5-week protocol. In contrast, blocking CP-mediated inactivation of C5a increased these disease measures. Thus, complement regulation by both plasma FH and CP to limit the quantity of active C5a is important in conditions where the humoral immune response is directed to a continuously present foreign antigen. Signaling through C5aR1 enhances the humoral immune response as well as the inflammatory response to ICs that have formed in glomeruli. Both effects are relevant even after disease has begun. Thus, pharmacological targeting of C5a in IC-mediated GN has potential clinical relevance.

No MeSH data available.