Expression of the CD2 activation epitope T11-3 (CD2R) on T cells in rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, and Lyme disease: phenotypic and functional analysis

Differential gene expression analysis of ankylosing spondylitis shows deregulation of the HLA-DRB, HLA-DQB, ITM2A, and CTLA4 genes

Background

Ankylosing spondylitis (AS) is a rare inflammatory disorder affecting the spinal joints. Although we know some of the genetic factors that are associated with the disease, the molecular basis of this illness has not yet been fully elucidated, and the genes involved in AS pathogenesis have not been entirely identified. The current study aimed at constructing a gene network that may serve as an AS gene signature and biomarker, both of which will help in disease diagnosis and the identification of therapeutic targets. Previously published gene expression profiles of 16 AS patients and 16 gender- and age-matched controls that were profiled on the Illumina HumanHT-12 V3.0 Expression BeadChip platform were mined. Patients were Portuguese, 21 to 64 years old, were diagnosed based on the modified New York criteria, and had Bath Ankylosing Spondylitis Disease Activity Index scores > 4 and Bath Ankylosing Spondylitis Functional Index scores > 4. All patients were receiving only NSAIDs and/or sulphasalazine. Functional enrichment and pathway analysis were performed to create an interaction network of differentially expressed genes.

Results

ITM2A, ICOS, VSIG10L, CD59, TRAC, and CTLA-4 were among the significantly differentially expressed genes in AS, but the most significantly downregulated genes were the HLA-DRB6, HLA-DRB5, HLA-DRB4, HLA-DRB3, HLA-DRB1, HLA-DQB1, ITM2A, and CTLA-4 genes. The genes in this study were mostly associated with the regulation of the immune system processes, parts of cell membrane, and signaling related to T cell receptor and antigen receptor, in addition to some overlaps related to the IL2 STAT signaling, as well as the androgen response. The most significantly over-represented pathways in the data set were associated with the “RUNX1 and FOXP3 which control the development of regulatory T lymphocytes (Tregs)” and the “GABA receptor activation” pathways.

Conclusions

Comprehensive gene analysis of differentially expressed genes in AS reveals a significant gene network that is involved in a multitude of important immune and inflammatory pathways. These pathways and networks might serve as biomarkers for AS and can potentially help in diagnosing the disease and identifying future targets for treatment.

CD2 Immunobiology

The glycoprotein CD2 is a costimulatory receptor expressed mainly on T and NK cells that binds to LFA3, a cell surface protein expressed on e.g., antigen-presenting cells. CD2 has an important role in the formation and organization of the immunological synapse that is formed between T cells and antigen-presenting cells upon cell-cell conjugation and associated intracellular signaling. CD2 expression is upregulated on memory T cells as well as activated T cells and plays an important role in activation of memory T cells despite the coexistence of several other costimulatory pathways. Anti-CD2 monoclonal antibodies have been shown to induce immune modulatory effects in vitro and clinical studies have proven the safety and efficacy of CD2-targeting biologics. Investigators have highlighted that the lack of attention to the CD2/LFA3 costimulatory pathway is a missed opportunity. Overall, CD2 is an attractive target for monoclonal antibodies intended for treatment of pathologies characterized by undesired T cell activation and offers an avenue to more selectively target memory T cells while favoring immune regulation.

Modulation of monocyte activation in patients with rheumatoid arthritis by leukapheresis therapy

One of the hallmarks in rheumatoid arthritis (RA) is the intense activation of the monocyte-macrophage system. In the present investigation, the modulation of blood monocyte activation was studied with regard to the secretion of cytokines and inflammatory mediators, and to the expression of cytokine receptors. Patients with severe active RA underwent repeated leukapheresis procedures that removed all circulating monocytes. Highly enriched monocyte preparations from the first and third leukapheresis were studied. There were striking differences between the two monocyte populations. Cells obtained from the first leukapheresis constitutively released large amounts of prostaglandin E2 (PGE2), neopterin, interleukin 1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha). In particular, IL-1 beta and neopterin production were further enhanced by stimulation with either interferon-gamma (IFN-gamma) or TNF-alpha without a synergistic effect. In contrast, cells derived from the third leukapheresis procedure showed a close to normal activation status with only low levels of cytokine and mediator production as well as a reduced response to cytokine stimulation. The number of the receptors for IFN-gamma and TNF-alpha was not changed between first and third leukapheresis. However, TNF-binding capacity was only detectable upon acid treatment of freshly isolated monocytes. A further upregulation was noted upon 24 h in vitro culture, suggesting occupation of membrane receptors and receptor down-regulation by endogenously produced TNF-alpha. Northern blot analysis of cytokine gene expression was in good correlation with the amount of mediators determined on the protein level. These data indicate that cells of the monocyte-macrophage system are already highly activated in the peripheral blood in RA patients with active disease. These cells can be efficiently removed by repeated leukapheresis and are replenished by monocytes that have, with respect to cytokine and mediator production, a considerably lower activation status.

Oligoclonal T cells in rheumatoid arthritis: identification strategy and molecular characterization of a clonal T-cell receptor

Immunodominant antigens in rheumatoid arthritis (RA) should induce an expansion of T cells bearing a corresponding T-cell receptor (TCR). We therefore analysed the TCR repertoire at the site of inflammation using two fundamentally different strategies. The total TCR repertoire was examined by generating 'representative' T-cell clone panels, which were subsequently tested for clonality by restriction mapping of the TCR beta gene locus. No clonality was detected in large T-cell clone panels generated with cells from three patients. However, when we selectively analysed the TCR repertoire of in vivo pre-activated, interleukin-2 (IL-2)-responsive T cells, significant T-cell/TCR clonality was found in 2 out of 4 patients. The clonal T cells represented a minority of the total T-cell population with an estimated frequency of 1 in 300 to 1 in 1000 cells. Molecular characterization of a clonal TCR and the use of a specific TCR V beta MoAb ruled out an over-representation of T cells bearing the same V beta element in the total T-cell population, rendering the involvement of super-antigens in the induction of T-cell clonality in this case unlikely.

Management of early inflammatory arthritis. Intervention with immunomodulatory agents: monoclonal antibody therapy

Over the last three years there has been a dramatic rise in the number of trials using monoclonal antibodies in the treatment of rheumatoid arthritis. So far, the numbers of patients treated in the individual studies have been small, and the study designs not comparable. All these trials have been conducted in a non-blinded, uncontrolled fashion. The patient populations tended to represent the severe end of the disease spectrum, being usually individuals for whom all other conventional and sometimes even unconventional experimental therapeutic approaches have failed. Clearly, therefore, larger controlled double blind studies in patients with less advanced stages of rheumatoid arthritis are needed. In the trials thus far, long-standing diseases afflicting the joints, usually with severe destruction, have frequently made clinical evaluation very difficult. Moreover, apparently with the exception of one or two reagents (16H5 and possibly B-F5) routine laboratory parameters which are helpful in determining disease activity such as CRP or the rheumatoid factor usually remain unaltered with anti-T cell therapy. In addition, in some individuals there was no clinical improvement despite sometimes severe CD4 cell depletion. The notion that the mere depletion of CD4+ cells is not sufficient to permanently suppress disease activity in autoimmune disease is further supported by studies carried out by Conolly and Wofsy in 1990. In a mouse lupus model, these investigators demonstrated that a small subpopulation of CD4+ T cells may be refractory to depletion by anti-CD4 and may be able to promote the full expression of the disease. Similar mechanisms could apply to certain individuals with human autoimmune disorders. Many additional questions remain open. The most important of these is which markers identify clinical responders to therapy. Attempts to correlate clinical response to the level of T cell depletion, modulation of the target antigens or in vitro functional assays so far have not yielded significant results. Other questions relate to the frequency of antibody administration and the amounts needed to permanently suppress disease activity. The initial hope based on animal experiments of inducing a permanent tolerance to certain antigens by anti-CD4 treatment has been clearly shown not to apply to rheumatoid arthritis. Even though there are individual variations, the efficacy of anti-T cell treatment tends to wear off after 3 or even 1 month, necessitating retreatment. Protocols will have to be designed for either longer treatment periods, repeated courses or more frequent single administrations.(ABSTRACT TRUNCATED AT 400 WORDS)