Complement regulatory proteins in kidneys of patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis

Abstract

The complement system activation is involved in the development of anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). The study aimed to investigate the expression of complement regulatory proteins (CRPs) CD46, CD55 and CD59 in kidneys of 51 AVV patients. The expression of CD46, CD55 and CD59 in kidneys was detected by immunohistochemistry and double immunofluorescence staining. The immunohistochemical examination revealed that expression of the three CRPs could be detected in the glomeruli and tubules of both AAV patients and normal controls. The expression levels of the three CRPs in glomeruli of patients with AAV were significantly lower than those of normal controls. The scores of CD46 and CD55 expression in the tubules of AAV patients were significantly lower than those of normal controls, while there was no significant difference between the scores of CD59 expression in tubules of AAV patients and those of normal controls. Among AAV patients, the expression level of CD46 in glomeruli correlated inversely with the proportion of normal glomeruli, while it correlated with tubular atrophy in renal interstitium (r = -0·305, P = 0·026; r = 0·330, P = 0·023, respectively). The expression levels of CD55 and CD59 in glomeruli correlated with the proportion of total crescents (r = 0·384, P = 0·006; r = 0·351, P = 0·011, respectively). Double immunofluorescence staining indicated that all three CRPs were expressed on endothelial cells, podocytes and mesangial cells in glomeruli. The expression levels of the three CRPs were dysregulated in kidneys of patients with AAV. The expression levels of CD46, CD55 and CD59 were associated with the severity of renal injury of AAV patients.

Keywords: anti-neutrophil cytoplasmic antibody; complement regulate proteins; pathology.

Figure 1

Immunohistochemistry staining for CD46, CD55 and CD59 in glomeruli of renal specimens. (a–c) Immunohistochemical staining of CD46, CD55 and CD59 in glomeruli of a normal control. (d–f) Immunohistochemical staining of CD46, CD55 and CD59 in glomeruli of patient with anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis. (g–i) Comparison of the mean optical density of CD46, CD55 and CD59 in glomeruli of patients with ANCA‐associated vasculitis to that of normal controls. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 2

Immunohistochemistry staining for CD46, CD55 and CD59 in the tubulointerstitial compartment of renal specimens. (a–c) Immunohistochemical staining of CD46, CD55 and CD59 in the tubulointerstitial compartment of a normal control. (d–f) Immunohistochemical staining of CD46, CD55 and CD59 in the tubulointerstitial compartment of patient with anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 3

Immunohistochemical staining of CD46, CD55 and CD59 on inflammatory cells in renal specimen of a patient with anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis. (a) Immunohistochemical staining of CD46 on inflammatory cells in kidney of anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis. (b) Immunohistochemical staining of CD55 on inflammatory cells in kidney of anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis. (c) Immunohistochemical staining of CD59 on inflammatory cells in kidney of anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 4

Association between the mean optical density of CD46, CD55 and CD59 in the glomeruli and clinicopathological parameters of patients with anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis. (a) Association between the mean optical density of CD46 in the glomeruli and the proportion of normal glomeruli. (b) Association between the mean optical density of CD55 in the glomeruli and the proportion of total crescents in renal specimens. (c) Association between the mean optical density of CD59 in the glomeruli and the proportion of total crescents in renal specimens. (d) Association between the mean optical density of CD46 and that of CD55 in the glomeruli. (e) Association between the mean optical density of CD46 and that of CD59 in the glomeruli.

Figure 5

Double immunofluorescence staining of CD46, CD55, CD59 and markers of three glomerular intrinsic cells in renal specimens of normal controls. (a–c) Co‐localization of CD46 (red) with CD31 (green), α‐smooth muscle actin (α‐SMA) (green) and podocalyxin (green) in glomeruli. (d–f) Co‐localization of CD55 (red) with CD31 (green), α‐SMA (green) and podocalyxin (green) in glomeruli. (g–i) Co‐localization of CD59 (red) with CD31 (green), α‐SMA (green) and podocalyxin (green) in glomeruli. The specific co‐staining for CD31, α‐SMA, podocalyxin and the three complement regulatory proteins (CRPs) was apparent in the merged picture as yellow/orange in glomeruli. [Colour figure can be viewed at wileyonlinelibrary.com]