Proteins of the Lectin Pathway of complement activation at the site of injury in subarachnoid hemorrhage compared with peripheral blood

Background: A subarachnoid hemorrhage (SAH) is a debilitating stroke. Activation of the lectin pathway (LP) of the complement system in SAH patients could worsen the prognosis; however, conflicting results have been reported. This potentially reflects that pathological changes at the site of injury are not reflected in peripheral blood.

Aims of the study: To measure the concentration of LP proteins in blood from the site of brain injury compared with peripheral blood in SAH patients, and to determine the concentration of LP proteins in cerebrospinal fluid (CSF).

Methods: We included 11 SAH patients undergoing aneurysm clipping or external ventricular drainage. Blood was collected from the site of injury and from a peripheral artery and/or CSF simultaneously. LP proteins were measured using time-resolved immunofluorometric assays.

Results: In all patients, the cerebral blood concentration of mannan-binding lectin, collectin liver-1 and collectin kidney-1, and mannan-associated serine proteases 1 and 2 were lower than in peripheral blood. The LP proteins were almost undetectable in CSF.

Conclusion: Lectin pathway protein concentrations measured in peripheral blood do not always reflect changes at the site of injury. For some proteins, more information could be obtained in blood from the site of injury when investigating pathogenic mechanisms.

Keywords: complement system; lectin pathway; subarachnoid hemorrhage.