IHC validation of T cell infiltration into engrafted tumors following immunotherapy. (A) IHC analysis of rag2^Δ/Δ, il2rga^−/− animals engrafted with U87 glioma cells engineered to express EGFP and EGFRvIII and then assessed for CD3⁺ T cell infiltration at 21 dpt. Animal receiving untransduced control T cells (top) or CD19 CAR T cell therapy (bottom) by IP injection on 7 dpt and 14 dpt. (B)rag2^Δ/Δ, il2rga^−/− animals engrafted with EGFP⁺ OVCAR-5 ovarian cancer cells that express endogenous EpCAM and monitored for CD3⁺ T cell infiltration at 21 dpt (IP therapy delivered on 7 dpt and 14 dpt). Animal received injection of CD8⁺ T cells along with EpCAM control antibody (top) or EpCAM-CD3 solitomab BiTE therapy (bottom). (C) Fish engrafted with EGFP⁺ breast cancer MDA–MB-231 cells that endogenously express EGFR and monitored for CD3⁺ T cell infiltration at 21 dpt. Animals were coadministered either EGFR control antibody (top) or EGFR-M14C along with CMV-specific T cells (bottom, IP injected on day 7 and 14 d). Scale bar is 50 µm.