However, negative selection as monitored by the deletion of Vβ5+ and Vβ3+ TCR SPs by the endogenous MMTV (mouse mammary tumour provirus) 6 and 8 superantigens in 14–16 day-old Ptpn2−/− (BALB/c) mice was not diminished, but rather modestly enhanced (Fig. 4b). The gene discussed is PTPN2; the disease is neoplasm.