Low activity of complement in the cerebrospinal fluid of the patients with various prion diseases

BACKGROUND The aim of this study was to analyze the state of activity and levels of complement in the cerebrospinal fluid (CSF) of patients with various prion diseases (PrDs). FINDINGS The proteomic data emphasized the levels of 20 known complement components found in the CSF of the sCJD panel that were lower than those found in the non-PrD panel. 50 % of the complement hemolytic activity (CH50) assays revealed significantly lower activity of complement in the CSF of the sCJD panel. The decreased levels of three key complement subunits, C3a/α, C4β, and C9 in the CSF of the sCJD panel were verified by Western blots. Furthermore, the CH50 values in the CSF of 136 sCJD, 39 gCJD, 22 FFI and 145 non-CJD patients were individually tested. Compared with the control of non-PrD, the CH50 value in the CSF specimens of various PrDs, especially in three subtypes of inherited PrDs, were significantly lower. Relationship analysis identified that the CH50 activity in the CSF was negatively associated with the protein 14-3-3 positive in the CSF. CONCLUSION These results indicate a silent complement system in the CSF of PrD patients.