Normal human enthesis harbours conventional CD4+ and CD8+ T cells with regulatory features and inducible IL-17A and TNF expression.

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-ß 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.

Spondyloarthropathies: progress and challenges.

The spondyloarthropathies are a group of human rheumatic disorders that are often associated with extra-articular features. Although a substantial number of studies is undertaken each year, many issues concerning the pathogenesis remain unanswered. There are several unresolved questions with regard to pathogenesis and treatment in spondyloarthropathies. First, the precise sites where inflammation originates within the joints have been a matter of controversy as enthesitis, synovitis and even bone marrow inflammation can occur during the course of spondyloarthropathies. In addition, the genetic predisposition involved in the origin of the close linkage between gut and joint inflammation, a prominent feature of SpA, has gathered much attention lately. Finally, whereas the effect of tumour necrosis factor (TNF) blockers in modulating inflammatory symptoms in SpA is well established, their ability to prevent new bone formation is much less certain. In addition, some marked differences appear to exist in the ability of the different TNF-blocking agents to modulate extra-articular disease manifestations.

Immune response to nonspecific and altered tissue antigens in soft tissue allografts.

Soft tissue allografts have many uses in orthopaedic surgery, including knee ligament reconstruction, hand tendon surgery, shoulder instability, and rotator cuff reconstruction. The predictable biologic incorporation of soft tissue allografts without rejection or fear of disease transmission continues to be a goal of basic science researchers. A review of the current knowledge if the immune system response to donor specific, nonspecific, and altered tissue antigens in soft tissue or tendon allografts is presented. An in vitro study was done in an attempt to decrease immunogenicity of a frozen bone-ligament graft by adding irrigation with Betadine scrub solution and hydrogen peroxide to the conventional storage process of freezing. Although the irrigation with cytotoxic agents would undoubtedly further decrease immunogenicity, it also decreased stiffness and maximum load by 15%. Whether this decreased strength and stiffness would compromise the incorporation and long term success of soft tissue allografts would need to be studied by in vitro experiments.

Immunoreactive neuropeptide nerves in ligamentous tissue in chronic shoulder pain.

Coracoacromial ligament and periligamentous fatty and loose connective tissue obtained during Neer's acromioplasty in patients with chronic painful rotator cuff tendinitis/impingement syndrome was studied for possible signs of inflammatory involvement and for the presence of neuropeptide-containing nerves, using routine histology and immunoperoxidase staining. No accumulations of inflammatory cells were found in the tissues studied. The dense ligamentous tissue proper was practically aneural, as was seen in staining for the generalized neuronal markers protein gene product 9.5 and synaptophysin. In contrast, the periligamentous fatty and loose connective tissue was innervated. Almost all nerves in such tissue contained C-flanking peptide of neuropeptide Y, whereas substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide-containing nerves were not found at all or were extremely rare. This suggests that the coracoacromial ligament is not a target of irritative inflammation. In the periligamentary sheath, nerves containing markers for the C-type nociceptive pain fibers were practically absent and all local nerves were postganglionic sympathetic vaso-regulatory nerves.