Natural killer cell activation after interferon administration in patients with metastatic renal cell carcinoma: An ultrastructural and immunohistochemical study

Objective: We studied the intralesional number of natural killer (NK) cells and the ultrastructural evidence of their activation in patients with metastatic renal cell carcinoma, after preoperative interferon (IFN) administration. Methods: Tumor sections from 10 patients with metastatic renal cell carcinoma who received preoperative IFN (5 MU x 3 days) and from 10 patients with renal cell carcinoma were obtained. The number of NK cells was estimated immunohistochemically in paraffin sections with the CD57 monoclonal antibody and their activation was evaluated ultrastructurally by routine electron microscopy processing. Results: The number of NK cells was increased in the tumors of the IFN-administered patients (5.3 cells vs. 1.6 in the controls, p = 0.03) while their ultrastructural features revealed activation and enhanced cytolytic activity, through facilitation of granule content release. Conclusions: IFN promotes the aggregation and activation of NK cells within the renal cell tumor, further strengthening the concept of its immunomodulatory acitivity.