Sex matters: Systemic complement activity of female C57BL/6J and BALB/cJ mice is limited by serum terminal pathway components

Abstract

Experimental mouse models have been extensively used to elucidate the role of the complement system in different diseases and injuries. Contribution of gender has revealed an intriguing gender specific difference; female mice often show protection against most complement driven injuries such as ischemia/reperfusion injury, graft rejection and sepsis. Interestingly, early studies to the mouse complement system revealed that female mice have very low total complement activity (CH50), which is related to androgen regulation of hepatic complement synthesis. Here, our aim was to understand at which level the female specific differences in mouse complement resides. We have used recently developed complement assays to study the functional activities of female and male mice at the level of C3 and C9 activation, and furthermore assayed key complement factor levels in serum of age-matched female and male C57BL/6 mice. Our results show that the female mice have normal complement cascade functionality at the level of C3 activation, which was supported by determinations of early complement factors. However, all pathways are strongly reduced at the level of C9 activation, suggesting a terminal pathway specific difference. This was in line with C6 and C9 measurements, showing strongly decreased levels in females. Furthermore, similar gender differences were also found in BALB/cJ mice, but not in CD-1 mice. Our results clearly demonstrate that the complement system in females of frequently used mouse strains is restricted by the terminal pathway components and that the perceived female specific protection against experimental disease and injury might be in part explained by the inability promote inflammation through C5b-9.

Properdin binds independent of complement activation in an in vivo model of anti–glomerular basement membrane disease

“…We have recently shown that female C57bl/6 mice have significantly reduced terminal complement pathway functionality. 39 In light of our results here, we can conclude that this residual complement activity results in prominent complement deposition in vivo when the injury is localized, such as in the glomeruli. Our results show an acute and transient infiltration of neutrophils, with simultaneous increase of serum MPO and SAP that precedes the full complement activation.…”

“…Measurement of functional mouse complement pathway activities was performed with an ELISA-based system as described previously. 39,45 In brief, human IgM-coated plates were used for CP, Mannan-coated plates for LP, and LPS-coated plates for AP ELISA. For CP and LP assessment plasma samples were diluted in MgCl 2and CaCl 2 -supplemented Veronal buffered saline, and for AP samples Veronal buffer supplemented with MgCl 2 and Ca 2þ -chelating EGTA.…”

Blocking Synthesis of the Variant Surface Glycoprotein Coat in Trypanosoma brucei Leads to an Increase in Macrophage Phagocytosis Due to Reduced Clearance of Surface Coat Antibodies

“…The complement used in these experiments was present in normal mouse serum (NMS) from the CD-1 mouse strain. Unlike many laboratory mouse strains, CD-1 mice have functional complement proteins of the terminal complement pathway, and have been shown to have functional serum complement activity of the classical, lectin and alternative pathways at the level of C9 activation [36]. To verify that the normal mouse serum from our CD-1 mice was indeed complement active, we showed activity of the classical pathway (requiring both antibodies and complement).…”

“…Complement-rich NMS was obtained from CD-1 mice, and is a kind gift of Prof. Paul Morgan (University of Cardiff). CD-1 mice are wild type for complement C5 as well as other components of the terminal complement pathway, and have functional serum complement activity of the classical, lectin and alternative complement pathways at the level of C9 activation (S1 Fig) [36, 63]. Alternatively, trypanosomes were incubated with a 1:5000 dilution of polyclonal rabbit anti-VSG221 antibody (gift of Jay Bangs, SUNY Buffalo) in the presence or absence of NMS for 30 minutes at 37°C.…”

Multicenter Alzheimer's and Parkinson's disease immune biomarker verification study

“…Findings for complement factors were also more pronounced in males than in females. In mouse models and human serum, complement activity is lower in females compared to males . Intriguingly, AD is more prevalent in females, while PD is more prevalent in males .…”