Immunopathological patterns in long-term renal allografts

Area of Science:

• Nephrology
• Immunology
• Transplantation

Background:

• Long-term renal allograft function is crucial for patient survival.
• Assessing graft health post-transplantation requires reliable diagnostic methods.
• Immunosuppression regimens aim to prevent rejection but can be associated with graft complications.

Purpose of the Study:

• To evaluate the utility of fine-needle aspiration biopsy (FNAB) cytology and immunohistology in assessing long-term renal allograft status.
• To correlate histological findings with immune markers and graft function.
• To differentiate between normal graft status, chronic changes, and active immune processes.

Main Methods:

• Analysis of 48 core needle biopsies and simultaneous FNABs from human renal allografts (12-158 months post-transplant).
• Conventional histology, immunohistochemistry for immune markers, and FNAB cytology were performed.
• Comparison of findings based on graft function (serum creatinine) and immunosuppression (azathioprine vs. cyclosporine).

Main Results:

• Excellent graft function (creatinine ≤ 120 μmol/L) correlated with normal FNAB cytology and immunohistology, regardless of immunosuppression.
• Reduced graft function (creatinine > 120 μmol/L) with normal histology or focal fibrosis typically showed normal FNAB/immunohistology.
• Five of 36 biopsies with reduced function exhibited immune activation patterns similar to acute rejection; chronic rejection showed varied immunopathology.

Conclusions:

• Inflammatory cell infiltration in long-term renal allografts suggests underlying pathology, even with normal histology.
• FNAB cytology and immunohistology can identify immune activation indicative of rejection in non-functioning grafts.
• Distinct immunopathological patterns in chronic rejection suggest diverse pathogenetic mechanisms requiring further investigation.