Circulating Immune Complexes and Complement Activation in Sensitized Kidney Transplant Recipients

Area of Science:

• Immunology
• Transplantation
• Nephrology

Background:

• Chronic antibody-mediated rejection is a primary cause of kidney transplant failure.
• The classical complement pathway, involving C1q binding to immune complexes, is implicated in this rejection process.
• Understanding complement activation markers like C1q immunocomplexes and CH50 is vital in sensitized kidney transplant recipients.

Purpose of the Study:

• To measure circulating C1q immunocomplexes (CIC-C1q) and complement activation (CH50) levels.
• To compare these levels in kidney transplant recipients (KTRs) with and without donor-specific antibodies (DSAs).
• To investigate the correlation between CIC-C1q levels and DSA titer in KTRs.

Main Methods:

• A cross-sectional study involving serum samples from KTRs with DSAs (n=14), KTRs without DSAs (n=28), and healthy controls (n=22).
• Enzyme immunoassay (EIA) kits (MicroVue CIC-C1q and MicroVue CH50) were used for quantification.
• Statistical analysis compared marker levels between groups and assessed correlations.

Main Results:

• KTRs with DSAs exhibited significantly higher CIC-C1q concentrations compared to controls and DSA-negative KTRs (p < 0.01).
• CIC-C1q levels showed a positive correlation with DSA titer.
• CH50 levels were significantly decreased in KTRs with DSAs compared to controls and DSA-negative KTRs (p < 0.01), indicating classical pathway activation.

Conclusions:

• Sensitized kidney transplant recipients with DSAs demonstrate elevated serum CIC-C1q levels.
• Increased classical pathway complement activation, evidenced by decreased CH50, is associated with DSAs in KTRs.
• These findings highlight the critical role of C1q immunocomplexes and complement activation in DSA-positive kidney transplant recipients, potentially contributing to chronic antibody-mediated rejection.