In particular, they revealed that pro-inflammatory RA SF, added to the culture medium of mesenchymal stem cells, was able to significantly inhibit the protein expression of NF-κB inhibitor, IκB, resulting in a consequent activation of the pathway; the authors assumed that the presence of different cytokines in SF, including TNF-α, was essential to regulate the activation of the signaling pathway, through the TNF/NF-κB axis. Here, NFKB1 is linked to rheumatoid arthritis.