When recombinant proteins go wrong: The hidden pitfall of recombinant protein contamination.

Recombinant proteins are critical tools in research; however, their purity is often assumed rather than verified, leading to potential experimental errors. This study aimed to investigate the inflammatory role of recombinant human IL-17F in dermal fibroblasts. Unexpectedly, we discovered with Western blot that recombinant IL-17F from the supplier was contaminated with IL-4, leading to unintended stimulatory effects such as STAT6 phosphorylation and gene induction of CCL26 and IL4R. This contamination led to misinterpretation of data, loss of research time, and erroneous conclusions about IL-17F activity. These findings underscore the critical need for stringent quality control in recombinant protein production and highlight the risks of relying on single-source suppliers. Researchers should remain cautious about potential contamination, ideally validating proteins from multiple suppliers. Our experience illustrates a broader requirement for suppliers to strengthen quality assurance measures, as contaminants can propagate misleading data in the literature and undermine research reproducibility.