Polarized monolayer cultures of human intestinal epithelial cell lines exposed to intractable proteins - In vitro hazard identification studies

•Intractable proteins did not produce adverse effects toward human intestinal epithelial cell (IEC) monolayers.•Intractable proteins do not appear to be inherently hazardous as a class of proteins.•In vitro methods of protein hazard identification require much less protein than studies with laboratory animals.•Inexpensive and readily available cells, reagents, and instruments can be used for protein hazard identification.