Early complementopathy after multiple injuries in humans

Abstract

After severe tissue injury, innate immunity mounts a robust systemic inflammatory response. However, little is known about the immediate impact of multiple trauma on early complement function in humans. In the present study, we hypothesized that multiple trauma results in immediate activation, consumption, and dysfunction of the complement cascade and that the resulting severe "complementopathy" may be associated with morbidity and mortality. Therefore, a prospective multicenter study with 25 healthy volunteers and 40 polytrauma patients (mean injury severity score = 30.3 ± 2.9) was performed. After polytrauma, serum was collected as early as possible at the scene, on admission to the emergency room (ER), and 4, 12, 24, 120, and 240 h post-trauma and analyzed for the complement profile. Complement hemolytic activity (CH-50) was massively reduced within the first 24 h after injury, recovered only 5 days after trauma, and discriminated between lethal and nonlethal 28-day outcome. Serum levels of the complement activation products C3a and C5a were significantly elevated throughout the entire observation period and correlated with the severity of traumatic brain injury and survival. The soluble terminal complement complex SC5b-9 and mannose-binding lectin showed a biphasic response after trauma. Key fluid-phase inhibitors of complement, such as C4b-binding protein and factor I, were significantly diminished early after trauma. The present data indicate an almost synchronical rapid activation and dysfunction of complement, suggesting a trauma-induced complementopathy early after injury. These events may participate in the impairment of the innate immune response observed after severe trauma.

Figure 1

(A) Complement function after multiple-injury as assessed by hemolytic serum activity (CH-50) determined from either healthy volunteers (n=25) or polytraumatized patients (n=40) with a mean ISS of 30.3 ± 2.9 at several time points after injury. *P<0.05, **P<0.01 between trauma group and healthy volunteers. (B) Comparison of complement hemolytic serum activity between healthy volunteers, survivors and non-survivors at the scene and at admission to the emergency room (ER).

Figure 2

(A) Generation of C3a as a function of time after polytrauma. *P<0.05, **P<0.01 between trauma group and healthy volunteers. (B) Inverse correlation between serum concentration of C3a in the emergency room (ER) and initial severity of traumatic brain injury as assessed by the Glasgow Coma Scale (GCS). (C) Subgroup analysis of serum C3a concentrations at the scene or at admission to the emergency room (ER) obtained from healthy volunteers, survivors and non-survivors.

Figure 3

(A) Trauma-induced generation of the anaphylatoxin C5a in serum of polytraumatized patients (n=40) versus healthy controls (n=25). *P<0.05, **P<0.01 versus healthy volunteers. (B) Inverse correlation of C5a serum concentration at the scene (25.1 ± 1.4 min after injury) and initial GCS reflecting primary traumatic brain injury. (C) Differences in C5a concentrations in serum obtained from polytrauma survivors and non-survivors early after injury.

Figure 4

Serum MBL levels as a function of time after polytrauma in similar samples. *P<0.05, **P<0.01 between trauma group and healthy volunteers.

Figure 5

(A) Concentration of the soluble terminal complement complex C5b-9 (SC5b-9) in otherwise non-activated serum from healthy volunteers or polytraumatized patients at different time points after injury. (B) Measurement of SC5b-9 formation in ex vivo zymosan (10 mg/ml)-activated serum obtained before from either healthy controls or multiple-injured patients at various time-points after trauma. *P<0.05, **P<0.01 versus healthy volunteers.

Figure 6

Assessment of fluid phase complement inhibitors early after trauma. Measurement of (A) C4BP-total, (B) C4BP-β serum concentrations from healthy volunteers or multiple-injured patients as a function of time after trauma. (C) Measurement of factor I concentrations in serum of healthy volunteers vs. multiple-injured patients at several time points post trauma. *P<0.05, **P<0.01 between trauma group and healthy volunteers.