A monoclonal antibody specific for human proinsulin (20G11) was generated and utilized for affinity purification mass spectrometry (AP-MS) for unbiased profiling of proinsulin protein:protein interactions in human islets. Half of each islet prep was treated with the cytokines IL1-beta and IFN-gamma. Immunoprecipitated proinsulin or control IgG immunoprecipitates from human islets were then subjected to state of the art mass spectrometry revealing a rich proinsulin biosynthetic network that is remarkably conserved across a diverse group of donors.