Abstract: Methods of attenuating an antigenic response in a mammal to one or more Type 1 diabetes related-antigens are provided. The method may result in delaying the onset of decreased pancreatic beta cell function in the mammal and/or at least delaying a reduction in serum C-peptide levels in the mammal The method comprises sublingually administering an effective amount of an insulin-related peptide to the mammal and commonly makes use of a sublingual formulation of an insulin-related peptide that includes an aqueous pharmaceutically acceptable carrier, e.g., an aqueous carrier which comprises at least about 30 vol. % glycerin.