1. INTRODUCTION
Takayasu arteritis (TA) is an uncommon systemic vasculitis that is
characterized by granulomatous inflammation of major blood vessels and
primarily involves the aorta and its major branches. Vascular
inflammation often leads
to
ischemia of organs and tissues supplied by the involved vessels and can
result in potentially life-threatening organ ischemia as well as aortic
regurgitation and pulselessness.1 The active stage of
TA is associated with the development of ischemic symptoms such as
coronary artery disease, stroke, and vision
loss.2Therefore, reliable disease activity assessment is important for
preventing TA progression and end-organ ischemic injury. The erythrocyte
sedimentation rate (ESR) and serum C-reactive protein (CRP) are the
biomarkers most commonly used to monitor TA disease activity; however,
as they may be influenced by several factors, they are neither sensitive
nor specific. In clinical practice, some patients may undergo
deterioration of vasculitis without elevation of CRP or ESR, and
increases in CRP or ESR are found in only approximately half of patients
with activeTA.3 Consequently, CRP and ESR do not
always show a positive association with TA disease activity or severe
vasculature impairment.4
Complement 1q (C1q) is an important promoter in the classical complement
pathway. C1q initiates and activates the complement cascade by
recognizing the complement-binding site of the antibody FC segment in
the IgG or IgM immune complex to clear antigen-antibody
complexes.5 C1q, which accounts for approximately 70%
of the C1 complex, can be deposited on the surface of apoptotic cells,
facilitating phagocytosis by phagocytes and protecting the body from the
inflammatory reactions.6 Serum C1q levels have
recently been evaluated in several autoimmune, such as lupus nephritis
(LN),7 pediatric systemic lupus erythematosus
(PSLE),8 juvenile idiopathic arthritis
(JIA)9 and idiopathic inflammatory myopathies
(IIMs).10 For example, Tan et al. found that the serum
C1q level was markedly reduced in LN patients compared with normal
controls, revealing a correlation with LN disease activity and renal
total activity index scores.7 In addition, Wu et al.
showed that the level of serum C1q in PSLE patients was significantly
lower than that in healthy children as well as in children with other
rheumatic diseases and that the level of serum C1q correlated negatively
with the disease active index.8 Furthermore, Gilliam
et al. reported that in JIA patients, mean serum levels of C1q were
significantly increased compared with those in healthy
children,9 and Li et al. indicated significant
increases in serum C1q levels in a PM/DM patient group with elevated ESR
compared with a group with normal ESR.10 However, the
serum C1q level and its association with disease activity have not been
investigated in TA patients. This study is the first to examine serum
C1q levels in Chinese TA patients and investigate their role in the
assessment of TA disease activity.