Incidence of autoimmune diabetes in NOD/Lt, NOD.PO+/–, and NOD.PO–/– mice. Data corresponds to 41 NOD.PO–/– females, 31 NOD.PO–/– males, 21 NOD.PO+/– females, seven NOD.PO+/– males, 114 NOD/Lt females, and 59 NOD/Lt males. See the text for statistics.