Is a human in vitro enthesitis model relevant to SpA-associated enthesitis? Response to: ‘Beware of wolves in sheep's clothing: immune cell plasticity and instability in health and disease’ by Alunno et al

We thank Alunno et al 1 for their comments on our paper reporting on the isolation and preliminary characterisation of normal human enthesis CD4+ and CD8+ conventional T-cells.2 Our work showed that up to 2% of CD4+ T cells were Th17 in nature as demonstrated by intracellular flow cytometry. We were unable to identify FOXP3+ Tregs at the enthesis, but these were readily demonstrable in peripheral blood from the same patients. Alunno and colleagues1 point towards the transdifferentiation between Th17s and Tregs that may occur in vivo and which can be modulated by pivotal spondyloarthritis (SpA) associated cytokines including TNF. Our results were generated in an artificial ‘in vitro enthesitis’ model, and we agree with the comments by Alunno et al 1 in regard to the role …