Evaluation of complement system proteins C3a, C5a and C6 in patients of endometriosis

Endometriosis is a disease that shows auto-immune and chronic characteristics, suggesting a role for proteins mediating immune interactions in its pathophysiology. The aim was to evaluate C3a and C5a for their role in inflammatory responses and C6 as the down-stream interactor following our previous findings on C5 mRNA expression changes in endometriosis [1].

Sera from 71 endometriosis patients and 77 women without endometriosis were taken. While the samples were taken only once from the controls, the patient samples were taken before, in 1st and in 7th days after laparoscopy. Levels of complement proteins C3a, C5a and C6 were measured with ELISA assays. MPV (Mean Platelet Volume), CRP (C-Reactive Protein) and NLR (Neutrophil-to-Leukocyte Ratio) were also analyzed from the retrospective data.

C6 levels of early-stage patients at postoperative 1st day were significantly higher than controls. Patients with high MPV measurements had significantly higher C3a (p < 0.0001) and C6 (p < 0.05) levels than controls at all times of measurement.

C6, an integral component of the membrane attack complex (MAC), could play a role at early disease-stage. The changes in levels of complement proteins and their relation to high MPV levels suggest a broader area of interplay for immune interactors in endometriosis. Although a bigger and longitudinal study design is needed to obtain more accurate results to evaluate these proteins as potential biomarkers, an important role of complement system within the pathophysiology of endometriosis is apparent.