C4d deposits in borderline rejection: an early marker for chronic renal dysfunction?

Area of Science:

• Nephrology
• Transplant Immunology
• Pathology

Background:

• Borderline rejection in renal allografts has a controversial impact on graft outcomes.
• C4d deposition and macrophage infiltration are key markers in transplant pathology.

Purpose of the Study:

• To investigate the presence and significance of C4d deposits and macrophage infiltration in renal biopsies diagnosed with borderline rejection.
• To determine the effect of these findings on long-term renal graft function.

Main Methods:

• Analysis of 31 renal transplant recipients with borderline rejection diagnoses.
• Morphological, C4d, and macrophage staining of initial and sequential biopsies.
• Comparison of biopsy findings with clinical data and graft function parameters.

Main Results:

• C4d-positive biopsies were associated with delayed graft function, higher acute tubular necrosis, capillaritis, and glomerular macrophage infiltration.
• Sequential biopsies revealed conversion from C4d-negative to C4d-positive status in some patients.
• Patients with C4d-positive biopsies exhibited significantly lower renal graft function at 6 months, 1 year, and 2 years post-transplantation.

Conclusions:

• C4d deposition in peritubular capillaries of borderline rejection renal biopsies is a significant indicator of poor renal allograft prognosis.
• Macrophage infiltration patterns also correlate with rejection severity and graft outcomes.