CD8A and neoplasm: It is noteworthy, that inter-model efficacy seemed to be overall associated with the immune status, since models with the highest number of CD4+ and CD8a+ cells according to combined IHC, flow cytometry and PET tumor-to-heart ratios (Sa1N, 4T1, CT26 and MC38), demonstrated significantly reduced tumor growth in response to Sym021 (Figure 3B-C).