The aim of this study was to examine the frequencies of IL-2-producing ILC3 and FoxP3+ Treg in SILP during the transition from prediabetes to diabetes in young and mature female NOD mice, during the development of disease in multiple low doses of streptozotocin (MLDS)-induced T1D, and to examine how treatment with broad-spectrum antibiotics before T1D induction affects these cell populations. This evidence concerns the gene FOXP3 and type 1 diabetes mellitus.