Ambrosino et al (2006) recently described treatment of Erbb2 transgenic mice with the CD25-specific mAb, PC61. These animals develop multiple mammary carcinomas as a result of overexpression of the Erbb2 oncogene. PC61-treated mice demonstrated reduced carcinoma multiplicity and a concomitant increase in immune responses to p185, the protein product of Errb2 (Ambrosino et al, 2006). The gene discussed is ESRRB; the disease is breast carcinoma.