Genetic and therapeutic targeting of properdin in mice prevents complement-mediated tissue injury
Yuko Kimura, Lin Zhou, Takashi Miwa, Wen-Chao Song
Yuko Kimura, Lin Zhou, Takashi Miwa, Wen-Chao Song
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Research Article Inflammation

Genetic and therapeutic targeting of properdin in mice prevents complement-mediated tissue injury

Abstract

The alternative pathway (AP) of complement activation is constitutively active and must be regulated by host proteins to prevent autologous tissue injury. Dysfunction of AP regulatory proteins has been linked to several human inflammatory disorders. Properdin is a positive regulator of AP complement activation that has been shown to extend the half-life of cell surface–bound C3 convertase C3bBb; it may also initiate AP complement activation. Here, we demonstrate a critical role for properdin in autologous tissue injury mediated by AP complement activation. We identified myeloid lineage cells as the principal source of plasma properdin by generating mice with global and tissue-specific knockout of Cfp (which encodes properdin) and by generating BM chimeric mice. Properdin deficiency rescued mice from AP complement–mediated embryonic lethality caused by deficiency of the membrane complement regulator Crry and markedly reduced disease severity in the K/BxN model of arthritis. Ab neutralization of properdin in WT mice similarly ameliorated arthritis development, whereas reconstitution of properdin-null mice with exogenous properdin restored arthritis sensitivity. These data implicate systemic properdin as a key contributor to AP complement–mediated injury and support its therapeutic targeting in complement-dependent human diseases.

Authors

Yuko Kimura, Lin Zhou, Takashi Miwa, Wen-Chao Song

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Figure 2

BM-derived cells are the major source of pathogenic properdin in K/BxN arthritis.

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BM-derived cells are the major source of pathogenic properdin in K/BxN a...
(A) Real-time PCR analysis of Cfp mRNA levels in BM cells of chimeric mice. Gapdh was used as an internal control, and values were normalized to those of WT mice. (B) Western blot analysis of properdin in the plasma (2 μl/lane) of chimeric mice. Numbers refer to individual mice. WT and Cfp–/– mouse plasmas were used as controls. Rabbit anti-mouse properdin serum was used as the primary Ab. (C) ELISA plate assay of LPS-induced AP complement activity in sera of chimeric mice. (D) K/BxN serum-induced arthritis in chimeric mice, as assessed by changes in ankle thickness (relative to day 0). *P < 0.05 versus WT→Cfp–/–, nonparametric Wilcoxon/Kruskal-Wallis test. (E) K/BxN serum-induced arthritis in chimeric mice, as assessed by clinical score. *P < 0.05 versus WT→Cfp–/–, nonparametric Wilcoxon/Kruskal-Wallis test. (F) Real-time PCR analysis of Cfp mRNA levels in splenic T (CD90+) and B (CD19+) lymphocytes and granulocytes/macrophages (CD11b+). All 3 types of cells were positively selected from splenocytes (pooled from 8 WT mice) by column purification. CD11b– cells were the leftover fraction from CD11b+ selection. Gapdh was used as an internal control, and values were normalized to that of total splenocytes (Spleen). Values represent mean ± SD of triplicate PCR assays.