TCR repertoire profiling revealed antigen-driven CD8+ T cell clonal groups shared in synovial fluid of patients with spondyloarthritis.

Spondyloarthritis (SpA) comprises a number of inflammatory rheumatic diseases with overlapping clinical manifestations. Strong association with several HLA-I alleles and T cell infiltration into an inflamed joint suggest involvement of T cells in SpA pathogenesis. In this study, we performed high-throughput T cell repertoire profiling of synovial fluid (SF) and peripheral blood (PB) samples collected from a large cohort of SpA patients. We showed that synovial fluid is enriched with expanded T cell clones that are shared between patients with similar HLA genotypes and persist during recurrent synovitis. Using an algorithm for identification of TCRs involved in immune response we discovered several antigen-driven CD8+ clonal groups associated with risk HLA-B*27 or HLA-B*38 alleles. We further show that these clonal groups were enriched in SF and had higher frequency in PB of SpA patients vs healthy donors, implying their relevance to SpA pathogenesis. Several of the groups were shared among patients with different SpAs that suggests a common immunopathological mechanism of the diseases. In summary, our results provide evidence for the role of specific CD8+ T cell clones in pathogenesis of SpA.

CD8+ T cells with characteristic T cell receptor beta motif are detected in blood and expanded in synovial fluid of ankylosing spondylitis patients.

Objective: The risk of AS is associated with genomic variants related to antigen presentation and specific cytokine signalling pathways, suggesting the involvement of cellular immunity in disease initiation/progression. The aim of the present study was to explore the repertoire of TCR sequences in healthy donors and AS patients to uncover AS-linked TCR variants. Methods: Using quantitative molecular-barcoded 5'-RACE, we performed deep TCR ß repertoire profiling of peripheral blood (PB) and SF samples for 25 AS patients and 108 healthy donors. AS-linked TCR variants were identified using a new computational approach that relies on a probabilistic model of the VDJ rearrangement process. Results: Using the donor-agnostic probabilistic model, we reveal a TCR ß motif characteristic for PB of AS patients, represented by eight highly homologous amino acid sequence variants. Some of these variants were previously reported in SF and PB of patients with ReA and in PB of AS patients. We demonstrate that identified AS-linked clones have a CD8+ phenotype, present at relatively low frequencies in PB, and are significantly enriched in matched SF samples of AS patients. Conclusion: Our results suggest the involvement of a particular antigen-specific subset of CD8+ T cells in AS pathogenesis, confirming and expanding earlier findings. The high similarity of the clonotypes with the ones found in ReA implies common mechanisms for the initiation of the diseases.

Circulating CD35(-)/CD49d(+) neutrophils in influenza virus infection patients.

Release of immature neutrophils from bone marrow into circulation accompanies acute inflammatory states. Previous studies have identified a number of antigens that are differentially expressed on mature neutrophils and immature forms. We analyzed expression of these antigens on circulating neutrophils of influenza virus infection patients. We identified a minor neutrophil subpopulation with decreased granularity and the antigen surface expression pattern (CD35(-)/CD49d(+)) which defines metamyelocytes. CD35(-)/CD49d(+) neutrophils were detected in 35% of the patients but not in healthy individuals and correlated positively with blood metamyelocyte count. The sorted CD35(-)/CD49d(+) neutrophils displayed morphological features of metamyelocytes. Compared with a major (CD35(+)/CD49d(-)) neutrophil subpopulation, CD35(-)/CD49d(+) neutrophils demonstrated significantly diminished functional capacities (both phagocytosis and respiratory burst). Thus, CD35(-)/CD49d(+) neutrophils represent a phenotypically and functionally distinct subpopulation of the cells and can potentially be used to quantify immature neutrophil release in inflammation.