Figure 5. Mouse humanization and resultant T cell infiltration and activity within tumors dictate nivolumab response.

(a) Human immune cells, including T cells (identified by dual redbrown staining) are much more abundant in both control and nivolumab-treated CUHN004 tumors implanted on very well-humanized mice (HM034, average 82.4% human bone marrow) than in comparable tumors on a more moderately humanized cohort (HM044, average 31.5% human bone marrow.) (b) T-cell mediated cell killing (identified by granzyme B, stained brown) in the vicinity of CD3+ T cells (stained red) is a measure of the activity of tumor-infiltrating T cells in these cohorts before and after nivolumab treatment. The T/C of 0.70 in the HM034 cohort suggests that, when T cells are present in great enough numbers within a tumor, nivolumab can enhance their ability to destroy tumor cells.