The importance of an effective immune response is also supported by the relative abundance of immune cell types in canine OS, namely that 3 of the 4 cell types with higher relative abundance in the PP group (GS-1 signature) are naïve or non-activated (naïve B-cells, naïve CD4 T, M0 macrophages) which may indicate an inadequate anti-tumor immune response. This evidence concerns the gene CD4 and neoplasm.