That the transduced M2 MΦs were recruited to and retained at the inflamed joint is entirely consistent with our previous observation that systemically injected genetically modified M2 MΦs expressing vitamin D-1α-hydroxylase (Cyp27b1) were rapidly recruited to and retained at the inflamed bowel in a mouse model of inflammatory bowel disease [44]. This evidence concerns the gene CYP27B1 and inflammatory bowel disease.