To examine the effect of ICB treatment on BrM at single-cell resolution, we purified CD45+ immune cells from 18 BrM samples, 8 of which were treated with ICB before surgery due to progression of peripheral/extracranial metastatic disease (Figure 1A and Supplemental Table 1A; supplemental material available online with this article; https://doi.org/10.1172/JCI169314DS1). Here, PTPRC is linked to metastatic neoplasm.