Fresh PBMC and tumor associated cells were isolated from a separate cohort of canine melanoma patients (P21-31; Supplementary Tables 1, 2) and tested by an abbreviated flow cytometry panel that included interrogation for CD3+ T cell subsets (CD4+, CD4-CD8-, and CD8+), FoxP3 and granzyme B (Supplementary Figure 7). Here, CD4 is linked to neoplasm.