Introduction: Delayed or Slow graft function (GD) immediately after deceased donor renal transplant (DDRTX) is often multifactorial in etiology with ischemia-reperfusion and immunological injury being most common. Recently, excess polyclonal free light chains (PFLCs) from increased production or decreased excretion has been shown to cause renal injury in non-transplant chronic kidney disease patients. It is conceivable that excess PFLC in ESRD patients can overwhelm proximal tubules immediately after transplant contributing to GD. The aim of this pilot study is to determine the degree of PFLC deposition by Immunohistochemical method (IHC) and tubular injury by Periodic Acid Schiff (PAS) staining in the proximal tubule of patients with GD.

Methods: A Retrospective study of 12 biopsies from 9 DDRTX and 6 controls (non-transplant, normal renal parenchyma) were stained for PFLC by IHC and renal injury by PAS method. The IHC staining were graded from 0 to 3+ (0, no stain, 3+ strong granular) and similarly injury score for PAS(0 to 3+, normal to loss of brush border). The results were compared between two groups.

Results: The Kappa IHC score was significantly higher in GD patients (2 to 3+; mean ± SE, 2.17 ± 0.11 AU [arbitrary units]) compared to controls (0 to 1+; mean ± SE, 0.67 ± 0.20) by unpaired student t test with p<0.05. Similarly, lambda also had higher score(1+ to 2+; 1.42 ± 0.15 AU) compared to controls (0.00 ± 0.00 AU, p<0.05, Figure1).The PAS stain showed significant decrease in brush borders suggestive of tubular injury in GD patients.

Conclusion: Our findings of excess PFLCs deposition in the proximal tubules of patients with GD post-DDRTX suggests that PFLCs could potentially cause added injury similar to CKD patients. Presently, the cause and effect is unclear. Prospective studies with serum and urine PFLC levels, and comparison with immediate graft function biopsies will determine the true impact of PFLCs on allograft function.

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