Targeting CD4+CD28− T cells by blocking CD28 co-stimulation

Retinal microvascular alterations in patients with active rheumatoid arthritis without cardiovascular risk factors: the potential effects of T cell co-stimulation blockade

Background

The evaluation of microvascular alterations might provide clinically useful information for patients with an increased cardiovascular (CV) risk, such as those with rheumatoid arthritis (RA), being the small artery remodeling the earliest form of target organ damage in primary CV diseases, such as arterial hypertension. The evaluation of retinal arterioles is a non-invasive technique aimed to identify an early microvascular damage, represented by the increase of the wall-to-lumen ratio (WLR) index. Abatacept (ABA), a T-cell co-stimulator blocker, is used to treat RA. A CV protective action was hypothesized for its peculiar mechanism of action in the modulation of T-cells, potentially involved in the pathogenesis of CV comorbidity. The study aimed to non-invasively investigate morphological characteristics of retinal arterioles in a cohort of RA patients treated with ABA.

Materials and methods

Seventeen RA patients [median (25th-75thpercentile) age = 58 (48-64) years, baseline 28-joint Disease Activity Score DAS28-C-reactive protein (DAS28-CRP) = 4.4 (3.9-4.6), body mass index (BMI) = 24.2 (23.4-26) kg/m2, rheumatoid factor positive:52.9%, anti-citrullinated peptide autoantibodies positive:76.5%] without known CV risk factors (arterial hypertension, diabetes, hypercholesterolemia, previous CV events, smoking) were evaluated by the adaptive optics imaging system of retinal arterioles before and every 6 months of therapy with ABA (T0, T6 and T12). Office blood pressure evaluation, 24-h ambulatory blood pressure monitoring and tissue-doppler echocardiography were also performed.

Results

A progressive significant reduction of the WLR of retinal arterioles was observed [T0 = 0.28 (0.25-0.30), T6 = 0.27 (0.24-0.31), T12 = 0.23 (0.23-0.26); p T0 vs. T6 = 0.414; p T6 vs. T12 = 0.02; p T0 vs. T12 = 0.009], without significant variations in other parameters. The T0-T12 reduction of WLR was correlated with that of DAS28-CRP (r:0.789; p = 0.005). Moreover, a significant reduction of diastolic office blood pressure and a trend for reduction of daily pressure measured by ambulatory monitoring were observed.

Conclusion

In a cohort of RA patients without known CV risk factors, a reduction of retinal microvascular alterations was demonstrated after treatment for 12 months with ABA, in parallel with the reduction of disease activity. These results might suggest the possibility of microvascular abnormalities regression induced by the immune system modulation.

Immune System and Microvascular Remodeling in Humans

Low-grade inflammatory processes and related oxidative stress may have a key role in the pathogenesis of hypertension and hypertension-mediated organ damage. Innate immune cells, such as neutrophils, dendritic cells, monocytes/macrophages, as well as unconventional T lymphocytes like γδ T cells contribute to hypertension and may trigger vascular inflammation. Adaptive immunity has been demonstrated to participate in elevation of blood pressure and in vascular and kidney injury. In particular, effector T lymphocytes (Th1, Th2, and Th17) may play a relevant role in promoting hypertension and microvascular remodeling, whereas T-regulatory lymphocytes may have a protective role. Effector cytokines produced by these immune cells lead to increased oxidative stress, endothelial dysfunction and contribute to target organ damage in hypertension. A possible role of immune cell subpopulations in the development and regression of microvascular remodeling has also been proposed in humans with hypertension. The present review summarizes the key immune mechanisms that may participate in the pathophysiology of hypertension-mediated inflammation and vascular remodeling; advances in this field may provide the basis for novel therapeutics for hypertension.

Comparative Study of Senescent Th Biomarkers in Healthy Donors and Early Arthritis Patients. Analysis of VPAC Receptors and Their Influence

Pro-inflammatory CD4⁺CD28⁻ T cells are characteristic of immunosenescence, but also of several autoimmune/inflammatory diseases. Vasoactive intestinal peptide (VIP) acts as an anti-inflammatory and immunomodulatory mediator on these cells. Our objective was to study the mutual influence between senescent Th cells and VIP axis in early arthritis (EA), comparing with non-EA donors. We characterized the correlation between senescent Th cells and clinic parameters of EA as well as the behavior of senescent Th biomarkers by real-time PCR. Clinical data were systematically recorded at baseline and after 6 months of follow-up. The number of CD4⁺CD28⁻ T cells measured by sorting is higher in patients who initially meet ACR classification criteria for rheumatoid arthritis (RA) compared to those who were classified as undifferentiated arthritis (UA). A slight positive correlation between EA CD4⁺CD28⁻ T cells and CRP or ESR and a negative correlation with bone mineral density were found. Th senescent biomarkers in EA CD4⁺CD28⁻ T cells were similar to donors, however some of them increased after 6 months of follow-up. VPAC receptors were analyzed by real-time PCR and immunofluorescence, and CD4⁺CD28⁻ T cells showed higher expression of VPAC₂ and lower of VPAC₁, VPAC₂ showing a significant increased expression in EA cells. Sorted CD4⁺CD28⁻ T cells were in vitro expanded in presence of VIP, wherein VIP increased senescent biomarker CD27, while it diminished CD57 or NKG2 senescent biomarkers. Our study demonstrates for the first time the existence of a link between senescent Th cells and the VIP axis.

Decreased circulating T regulatory lymphocytes in obese patients undergoing bariatric surgery

OBJECTIVE

It has been previously demonstrated that T lymphocytes may be involved in the development of hypertension and microvascular remodeling, and that circulating T effector lymphocytes may be increased in hypertension. In particular, Th1 and Th 17 lymphocytes may contribute to the progression of hypertension and microvascular damage while T-regulatory (Treg) lymphocytes seem to be protective in this regard. However, no data is available about patients with severe obesity, in which pronounced microvascular alterations were observed.

DESIGN AND METHODS

We have investigated 32 severely obese patients undergoing bariatric surgery, as well as 24 normotensive lean subjects and 12 hypertensive lean subjects undergoing an elective surgical intervention. A peripheral blood sample was obtained before surgery for assessment of CD4+ T lymphocyte subpopulations. Lymphocyte phenotype was evaluated by flow cytometry in order to assess T-effector and Treg lymphocytes.

RESULTS

A marked reduction of several Treg subpopulations was observed in obese patients compared with controls, together with an increased in CD4+ effector memory T-effector cells.

CONCLUSION

In severely obese patients, Treg lymphocytes are clearly reduced and CD4+ effector memory cells are increased. It may be hypothesized that they might contribute to the development of marked microvascular alterations previously observed in these patients.

Expansions of Cytotoxic CD4+CD28- T Cells Drive Excess Cardiovascular Mortality in Rheumatoid Arthritis and Other Chronic Inflammatory Conditions and Are Triggered by CMV Infection

A large proportion of cardiovascular (CV) pathology results from immune-mediated damage, including systemic inflammation and cellular proliferation, which cause a narrowing of the blood vessels. Expansions of cytotoxic CD4⁺ T cells characterized by loss of CD28 (“CD4⁺CD28⁻ T cells” or “CD4⁺CD28^null cells”) are closely associated with cardiovascular disease (CVD), in particular coronary artery damage. Direct involvement of these cells in damaging the vasculature has been demonstrated repeatedly. Moreover, CD4⁺CD28⁻ T cells are significantly increased in rheumatoid arthritis (RA) and other autoimmune conditions. It is striking that expansions of this subset beyond 1–2% occur exclusively in CMV-infected people. CMV infection itself is known to increase the severity of autoimmune diseases, in particular RA and has also been linked to increased vascular pathology. A review of the recent literature on immunological changes in CVD, RA, and CMV infection provides strong evidence that expansions of cytotoxic CD4⁺CD28⁻ T cells in RA and other chronic inflammatory conditions are limited to CMV-infected patients and driven by CMV infection. They are likely to be responsible for the excess CV mortality observed in these situations. The CD4⁺CD28⁻ phenotype convincingly links CMV infection to CV mortality based on a direct cellular-pathological mechanism rather than epidemiological association.

Relationship Between Different Subpopulations of Circulating CD4+ T-lymphocytes and Microvascular Structural Alterations in Humans

BACKGROUND

Different components of the immune system, including innate and adaptive immunity (T-effector lymphocytes and T-regulatory lymphocytes-TREGs) may be involved in the development of hypertension. In addition, it was demonstrated in animal models that TREGs may prevent angiotensin II-induced hypertension and vascular injury/inflammation. However, no data are presently available in humans about possible relationships between T-lymphocyte subtypes and microvascular structural alterations.

METHODS

For this purpose, in the present study, we enrolled 24 normotensive subjects and 12 hypertensive patients undergoing an elective surgical intervention. No sign of local or systemic inflammation was present. All patients underwent a biopsy of subcutaneous fat during surgery. Subcutaneous small resistance arteries were dissected and mounted on a wire myograph and the media to lumen ratio (M/L) was calculated. In addition, retinal arteriolar structure was evaluated noninvasively by scanning laser Doppler flowmetry. Capillary density in the nailfold, dorsum of the finger, and forearm were evaluated by videomicroscopy. A peripheral blood sample was obtained before surgery for assessment of T-lymphocyte subpopulations by flow cytometry.

RESULTS

Significant negative correlations were observed between indices of microvascular structure (M/L of subcutaneous small arteries and wall to lumen ratio of retinal arterioles) and circulating TREG lymphocytes. A direct correlation was observed between M/L of subcutaneous small arteries and circulating Th17 lymphocytes. In addition, total capillary density was correlated with a TREG effector memory subpopulation.

CONCLUSION

Our data suggest that some lymphocyte subpopulations may be related to microvascular remodeling, confirming previous animal data, and opening therapeutic possibilities.

Reduced T-cell repertoire restrictions in abatacept-treated rheumatoid arthritis patients

Background

CD28^neg T cells, which display functional characteristic of oligoclonally expanded cytotoxic memory T lymphocytes, are believed to be pathologically relevant in rheumatoid arthritis manifestation. The CD28 co-stimulation blockade by abatacept can prevent the generation of CD28^neg T-cell populations in these patients.

Methods

Samples were obtained before and after 12 months of abatacept therapy. T-cell phenotype and T-cell receptor diversity were evaluated by flow cytometry and complementarity-determining region-3 spectratyping, respectively, while telomerase reverse-transcriptase gene level was measured by real-time PCR.

Results

Abatacept induces a decrease of the percentage and number of CD4⁺CD28^neg T cells and a reduction of T-cell repertoire restrictions; these features are directly correlated. Thymic output and telomerase activity are not modified by the therapy.

Conclusions

Abatacept-induced decrease of peripheral T-cell repertoire restrictions can due to a reduced generation of senescent, chronically stimulated CD4⁺CD28^neg T cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0363-2) contains supplementary material, which is available to authorized users.

Abatacept reduces levels of switched memory B cells, autoantibodies, and immunoglobulins in patients with rheumatoid arthritis

OBJECTIVE

Abatacept (ABA) is a chimeric molecule, able to block the CD28-mediated costimulatory pathway. To evaluate the hypothesis that, through this mechanism of action, ABA may down-modulate the immune responses of B lymphocytes in rheumatoid arthritis (RA), we investigated the serum levels of immunoglobulins (Ig), free light chains (FLC), anticitrullinated protein antibodies (ACPA), and rheumatoid factor (RF), as well as the number of B lymphocytes differentiated into post-switch memory cells in patients treated with ABA.

METHODS

The serum levels of Ig, FLC, different ACPA, RF isotypes, and the B cell phenotype were longitudinally evaluated in 30 patients with RA treated with ABA.

RESULTS

At baseline, the proportion of total and post-switch memory B cells was lower in RA than in healthy individuals. After 6 months of ABA treatment we observed significant reductions of serum levels of IgG, IgA, and IgM, as well as FLC, with a normalization in many patients who had initially abnormal values. A significant reduction of the titers of IgG- and IgA-ACPA, as well as of IgM-, IgA-, and IgG-RF was also observed. A decrease of autoantibodies below the upper limits of normal values was found in 2 of 26 patients (8%) initially seropositive for IgG-ACPA, 1 of 14 (7%) for IgA-ACPA, 5 of 22 (23%) for IgM-RF, 7 of 22 (30%) for IgA-RF, and 5 of 16 (31%) for IgG-RF. After treatment, the proportion of circulating post-switch memory B cells was also further significantly decreased.

CONCLUSION

ABA treatment in patients with RA can reduce signs of polyclonal B cell activation, inducing a trend toward normalization of serum levels of different classes of Ig and of FLC, decreasing titers of ACPA and RF, and percentages of post-switch memory B cells.