As the autoimmune phenotype in Ctla4−/− mice occurs at a young age,25,26 and targeted mutation of the Ctla4 gene in adult mice leads to less severe autoimmune disease,27 we reasoned that mice may be most susceptible to anti-CTLA-4 mAbs if they are administrated at a young age. The gene discussed is CTLA4; the disease is autoimmune disease.