Freshly harvested tumors from Trem1+/+and Trem1-/- mice were pooled separately into 2 groups to maximize the isolation of tumor infiltrating myeloid cells. Tumors were gently dissociated using the gentleMACS Octo Dissociator with Heaters (Miltenyi Biotech). Single-cell suspensions of tumor cells were purified by incubation with CD11b Microbeads (Miltenyi Biotec, cat. no. 130-049-601) as per the manufacturer's instructions to enrich the tumor-infiltrating myeloid cells. Quality and quantity of cells were assessed under the microscope by trypan blue staining, and dead cells were removed using theDead Cell Removal Kit (STEMCELL, cat. no. 17899) as per the manufacturer's instructions. Nuclei acid extraction was performed following the manufacturer's instructions (10x Genomics, as part of the Chromium Single Cell 3' v3.1). We assayed up to 4200 isolated CD45+CD11b+ cells from the TME of the B16F10 melanoma model with a coverage rate of 18,854 genes per cell. scRNA-seq libraries were generated using ChromiumNext GEM Single Cell 3' Reagent kit v3.1 (10x Genomics) according to the manufacturer's protocol.