Immune cell phenotyping of clear cell renal cell carcinoma.

511Background: Clear cell renal cell carcinoma (ccRCC) tumors develop mechanisms that impair function and/or prevent entry of the host infiltrating immune cells (immune exclusion) within the tumor microenvironment. The goal of immunotherapy is to overcome this immune resistance. We aim to characterize the T−cell populations in a cohort of largely untreated high risk patients with ccRCC. Methods: We prospectively collected ccRCC tumor and adjacent normal kidney (NK) from patients undergoing surgical resection at our institution from 6/2015-8/2016. Immune cell phenotyping was performed by immune cell staining of single cell suspensions. Analysis of immune cell populations were determined by CD45+ staining and corresponding proportions of different T−cell populations (CD3+, CD4+, CD4+Treg, and CD8+ T cells). Staining for CD4+Treg was not available for two patients. Student t−test was utilized to compare the immune populations between tumor and adjacent NK tissue. Analysis was also conducted by stratifying pa...