CD8A and melanoma: Analysis of canine melanoma patients (n = 20; P1-20) revealed decreased frequencies of CD4+ T cells compared to healthy controls (n = 20, p = 0.039) (Figure 3A); however, no significant differences for frequencies of CD8+ and CD4-CD8- T cell subsets in blood were detected between patients and controls (n = 20) (Supplementary Figures 2A,B).