Chemokines and their receptors determine the distribution of leukocytes within tissues in health and disease. We have studied the role of the constitutive chemokine receptor CXCR4 and its ligand, stromal-derived factor-1 (SDF-1) in the perivascular accumulation of T cells in rheumatoid arthritis. We show that synovial T cells, which are primed CD45RO+CD45RBdull cells and consequently not expected to express constitutive chemokine receptors, have high levels of the chemokine receptor CXCR4. Sustained expression of CXCR4 was maintained on synovial T cells by specific factors present within the synovial microenvironment. Extensive screening revealed that TGF-β isoforms induce the expression of CXCR4 on CD4 T cells in vitro. Depletion studies using synovial fluid confirmed an important role for TGF-β1 in the induction of CXCR4 expression in vivo. The only known ligand for CXCR4 is SDF-1. We found SDF-1 on synovial endothelial cells and showed that SDF-1 was able to induce strong integrin-mediated adhesion of synovial fluid T cells to fibronectin and ICAM-1, confirming that CXCR4 expressed on synovial T cells was functional. These results suggest that the persistent induction of CXCR4 on synovial T cells by TGF-β1 leads to their active, SDF-1-mediated retention in a perivascular distribution within the rheumatoid synovium.

Pathological processes involved in the initiation of rheumatoid synovitis remain unclear. We undertook the present study to identify immune and stromal processes that are present soon after the clinical onset of rheumatoid arthritis (RA) by assessing a panel of T cell, macrophage, and stromal cell related cytokines and chemokines in the synovial fluid of patients with early synovitis. Synovial fluid was aspirated from inflamed joints of patients with inflammatory arthritis of duration 3 months or less, whose outcomes were subsequently determined by follow up. For comparison, synovial fluid was aspirated from patients with acute crystal arthritis, established RA and osteoarthritis. Rheumatoid factor activity was blocked in the synovial fluid samples, and a panel of 23 cytokines and chemokines measured using a multiplex based system. Patients with early inflammatory arthritis who subsequently developed RA had a distinct but transient synovial fluid cytokine profile. The levels of a range of T cell, macrophage and stromal cell related cytokines (e.g. IL-2, IL-4, IL-13, IL-17, IL-15, basic fibroblast growth factor and epidermal growth factor) were significantly elevated in these patients within 3 months after symptom onset, as compared with early arthritis patients who did not develop RA. In addition, this profile was no longer present in established RA. In contrast, patients with non-rheumatoid persistent synovitis exhibited elevated levels of interferon-γ at initiation. Early synovitis destined to develop into RA is thus characterized by a distinct and transient synovial fluid cytokine profile. The cytokines present in the early rheumatoid lesion suggest that this response is likely to influence the microenvironment required for persistent RA.

Objective To test the hypothesis that the formation of ectopic germinal center (GC)–like structures in Sjögren's syndrome (SS) is associated with the ectopic expression of the constitutive lymphoid tissue–homing chemokines B cell–attracting chemokine 1 (BCA‐1; or, CXCL13) and stromal cell–derived factor 1 (SDF‐1; or, CXCL12). Methods Immunohistochemical and immunofluorescence analysis was used to determine the expression of the constitutive chemokines BCA‐1 (CXCL13) and SDF‐1 (CXCL12) in salivary glands from 5 SS patients and 3 non‐SS patients. In addition, the expression of their respective receptors (CXCR5 and CXCR4) was examined on infiltrating lymphocytes. Human tonsil was used as a positive control for secondary lymphoid tissue. Results BCA‐1 (CXCL13) was expressed within lymphoid aggregates in SS, which shared many structural features with GCs in tonsil. BCA‐1 (CXCL13) was completely absent in control biopsy samples from patients who did not have SS. High levels of BCA‐1 (CXCL13) were also found on endothelial cells in salivary glands from SS patients. Diseased SS tissue was infiltrated by CXCR5‐expressing B cells which organized into GC‐like clusters. In complete contrast, SDF‐1 (CXCL12), a constitutive chemokine involved in leukocyte retention within lymphoid tissue, was expressed by epithelial cells in both diseased and control samples. The chemokine receptor for SDF‐1, CXCR4, was expressed on T cells that accumulated in a periductal distribution in diseased tissue. Conclusion The ectopic expression of BCA‐1 (CXCL13) on endothelial cells and within GC‐like structures, together with the strong expression of SDF‐1 (CXCL12) on ductal epithelial cells, is a unique feature of inflamed glands in SS. By creating a local microenvironment supportive of focal B cell aggregation and differentiation, with structural features that are remarkably similar to GCs, BCA‐1 (CXCL13) and SDF‐1 (CXCL12) may contribute to the excessive production of high‐affinity, class‐switched autoantibodies and to the high incidence of B cell lymphomas classically associated with SS.

Application of multiplex bead immunoassays has allowed us to identify distinct patterns of cytokines that relate to both clinical disease and the cellular infiltrates present. Bioinformatics analysis allowed identification of cytokines that differentiate idiopathic uveitis from noninflammatory control AqH and are likely to be important for the pathogenesis of uveitis.

Immunity declines during aging, however the mechanisms involved in this decline are not known. In this study, we show that cutaneous delayed type hypersensitivity (DTH) responses to recall antigens are significantly decreased in older individuals. However, this is not related to CC chemokine receptor 4, cutaneous lymphocyte-associated antigen, or CD11a expression by CD4+ T cells or their physical capacity for migration. Instead, there is defective activation of dermal blood vessels in older subject that results from decreased TNF-α secretion by macrophages. This prevents memory T cell entry into the skin after antigen challenge. However, isolated cutaneous macrophages from these subjects can be induced to secrete TNF-α after stimulation with Toll-like receptor (TLR) 1/2 or TLR 4 ligands in vitro, indicating that the defect is reversible. The decreased conditioning of tissue microenvironments by macrophage-derived cytokines may therefore lead to defective immunosurveillance by memory T cells. This may be a predisposing factor for the development of malignancy and infection in the skin during aging.

Differential cytokine levels support tears as a useful indicator of immune mechanisms occurring during AC. The striking similarities in chemokine profiles between tears and fibroblasts suggest these cells as likely sources of chemokines in tears.

Using HLA class I-viral epitope tetramers to monitor herpes virus-specific CD8+ T cell responses in humans, we have shown that a significant fraction of responding cells revert from a CD45RO+ to a CD45RA+ state after priming. All tetramer-binding CD45RA+ cells, regardless of epitope specificity, expressed a phenotype LFA-1highCCR7low that was stable for at least 10 years in infectious mononucleosis patients and indefinitely in asymptomatic carriers. CD8+CD45RA+LFA-1high cells were not present in cord blood but in adults account for up to 50% of CD8+CD45RA+ cells. These CD45RA+LFA-1high cells have significantly shorter telomeres than CD45RA+LFA-1low cells, suggesting that the latter represent a naive population, while the former are memory cells. CD45RA+ memory cells are a stable population of noncycling cells, but on stimulation they are potent producers of IFN-γ, while naive CD8+ cells produce only IL-2. The chemokine receptor profile and migratory potential of CD45RA+ memory cells is very similar to CD45RO+ cells but different to naive CD8 cells. In accord with this, CD45RA+ memory cells were significantly underrepresented in lymph nodes, but account for virtually all CD8+CD45RA+ T cells in peripheral tissues of the same individuals.

No abstract