Life tables of diabetes development. a, Lack of progression to diabetes of NOD mice lacking both insulin native genes. b, c, Lack of difference in progression to diabetes for speed congenic female NOD mice with control regions from the 129 mouse surrounding the insulin genes (insulin 1 region (b); insulin 2 region (c)). d, Progression to diabetes of the four transgenic founder strains with the mutated preproinsulin gene on NOD background (insulin 1+/+, insulin 2+/+, transgene+). Founder strain F was significantly different (P < 0.01) from the others. e, NOD.SCID recipients of splenocytes from mice lacking both native insulin genes had delayed progression to diabetes compared with insulin 1+, insulin 2+ mice (P < 0.02). ins, insulin; Tg, transgene.