Superimposition of canIL-13 and huIL-13 molecules, (3D reconstruction using JMol), A. Purified canIL-13.E13K and canIL-13.E13K cytotoxin, (10% SDS-PAGE), B and C. Activation of TF-1 cells proliferation by cytokines, D. Cytotoxicity of canIL-13 cytotoxin and its neutralization on BTCOE 4795 human GBM cells, E. P<0.015 and <0.007 for differences between the cytokines (in D) and the cytotoxin killing vs. neutralization with canIL-13.E13K alone (in E) using an unpaired t-test. Cytotoxicity of canIL-13.E13K cytotoxin on canine GBM G06-A cells, F. Cytotoxicity of canIL-13.E13K cytotoxin on human GBM established (U-251 MG), G, and low passage human GBM cells (BTCOE 4795), H. CTL – control. Vertical bars represent SEM and if not seen, they are smaller than the points.