@article {Watad1044, author = {Abdulla Watad and Hannah Rowe and Tobias Russell and Qiao Zhou and Lisa K Anderson and Almas Khan and Robert Dunsmuir and Peter Loughenbury and Vishal Borse and Abhay Rao and Peter A Millner and Nicola Luigi Bragazzi and Howard Amital and Richard Cuhtbert and Miriam Wittmann and Kassem Sharif and Tony Kenna and Matthew A Brown and Darren Newton and Charlie Bridgewood and Dennis G McGonagle}, title = {Normal human enthesis harbours conventional CD4+ and CD8+ T cells with regulatory features and inducible IL-17A and TNF expression}, volume = {79}, number = {8}, pages = {1044--1054}, year = {2020}, doi = {10.1136/annrheumdis-2020-217309}, publisher = {BMJ Publishing Group Ltd}, abstract = {Background The human enthesis conventional T cells are poorly characterised.Objectives To study the biology of the conventional T cells in human enthesis.Methods CD4+ and CD8+ T cells were investigated in 25 enthesis samples using immunofluorescence, cytometrically, bulk RNAseq and quantitative real-time PCR following anti-CD3/CD28 bead stimulation to determine interleukin (IL)-17A and tumour necrosis factor (TNF) levels. T-cell receptor (TCR) repertoires were characterised and a search for putative T-cell reactivity was carried out using TCR3 database. The impact of pharmacological antagonism with retinoic acid receptor-related orphan nuclear receptor gamma t inhibitor (RORγti), methotrexate and phosphodiesterase type 4 inhibitor (PDE4i) was investigated.Results Immunofluorescence and cytometry suggested entheseal resident CD4+ and CD8+ T cells with a resident memory phenotype (CD69+/CD45RA-) and tissue residency gene transcripts (higher NR4A1/AhR and lower KLF2/T-bet transcripts). Both CD4+ and CD8+ T cells showed increased expression of immunomodulatory genes including IL-10 and TGF-β compared with peripheral blood T cells with entheseal CD8+ T cells having higher CD103, CD49a and lower SIPR1 transcript that matched CD4+ T cells. Following stimulation, CD4+ T cells produced more TNF than CD8+ T cells and IL-17A was produced exclusively by CD4+ T cells. RNAseq suggested both Cytomegalovirus and influenza A virus entheseal resident T-cell clonotype reactivity. TNF and IL-17A production from CD4+ T cells was effectively inhibited by PDE4i, while RORγti only reduced IL-17A secretion.Conclusions Healthy human entheseal CD4+ and CD8+ T cells exhibit regulatory characteristics and are predicted to exhibit antiviral reactivity with CD8+ T cells expressing higher levels of transcripts suggestive of tissue residency. Inducible IL-17A and TNF production can be robustly inhibited in vitro.}, issn = {0003-4967}, URL = {https://ard.bmj.com/content/79/8/1044}, eprint = {https://ard.bmj.com/content/79/8/1044.full.pdf}, journal = {Annals of the Rheumatic Diseases} }