Specific for human proinsulin (different epitopes generated by the interactions between insulin and C-peptide parts of prohormone), Kd >3 x 10-8 M. Not cross-reacts with human, bovine and porcine insulin, bovine and porcine proinsulin, and human C-peptide. Can be used for detection of human proinsulin in two-site enzyme immunoassay, recommended pairs (coating - conjugate): 1D6 - 7F8, 8E2 Hytest Cat.# 2I1, D6C4 or D3E7 Hytest Cat.# 2IP10; for specific immunosorbtional removal of proinsulin molecules (with immobilized 1D6/1D3 MAbs) from serum samples before the measurement of insulinic C-peptide.