To test whether IRMs from insulitis and T1D-free mice are functionally immunoregulatory, we performed mixed lymphocyte reactions (MLRs) with IRM, IRDC or splenic DC stimulator cells from bm12 mice (I-Abm12) and FoxP3/GFP-CD4+ T cells from ABM TCR transgenic mice. This evidence concerns the gene CD4 and type 1 diabetes mellitus.