The transplanted liver can modulate the recipient immune system to induce tolerance after transplantation. This phenomenon was observed nearly five decades ago. Subsequently, the liver's role in multivisceral transplantation was recognized, as it has a protective role in preventing rejection of simultaneously transplanted solid organs such as kidney and heart. The liver has a unique architecture and is home to many cells involved in immunity and inflammation. After transplantation, these cells migrate from the liver into the recipient. Early studies identified chimerism as an important mechanism by which the liver modulates the human immune system. Recent studies on human T-cell subtypes, cytokine expression, and gene expression in the allograft have expanded our knowledge on the potential mechanisms underlying immunomodulation. In this article, we discuss the privileged state of liver transplantation compared to other solid organ transplantation, the liver allograft's role in multivisceral transplantation, various cells in the liver involved in immune responses, and the potential mechanisms underlying immunomodulation of host alloresponses.

Percutaneous access and antegrade intervention remains the gold standard in the management of renal and ureteral complications in the renal transplant recipient. Current techniques with large nephrostomy sheaths and instrumentation carry significant morbidity in this patient population. We present our experience with a modification of the standard nephroscopic approach using a smaller (16F) O'Brien suprapubic peel-away introducer and sheath to access the allograft renal pelvis and allow manipulation with a smaller-caliber endoscope, with the purpose of attaining similar treatment outcomes with less morbidity in this subset of patients. Fourteen renal transplant patients with indications for antegrade management of renal or proximal ureteral complications had successful endoscopic intervention through the smaller sheaths without suffering any intraoperative or postoperative complications at a mean follow-up of 22 months (range 8-37 months). The mean operative time was 140 minutes (33-190 minutes), which is not significantly different from our operative time using standard instrumentation.

Renal transplant patients with urologic complications can be managed safely with percutaneous techniques. The development of renal calculi in transplanted kidneys is uncommon, but in these cases complications such as infection and urinary tract obstruction with impairment of graft function can occur. We report 2 cases managed successfully with percutaneous nephrolithotomy.