Evaluation of CD4(+)CD25(+)FoxP3(+) T cell populations, IL-10 production, and their correlation with clinical and biochemical parameters in sickle cell anemia patients with leg ulcers

Controversies in the pathophysiology of leg ulcers in sickle cell disease

Patients with sickle cell disease (SCD) often experience painful vaso-occlusive crises and chronic haemolytic anaemia, as well as various acute and chronic complications, such as leg ulcers. Leg ulcers are characterized by their unpredictability, debilitating pain and prolonged healing process. The pathophysiology of SCD leg ulcers is not well defined. Known risk factors include male gender, poor social conditions, malnutrition and a lack of compression therapy when oedema occurs. Leg ulcers typically start with spontaneous pain, followed by induration, hyperpigmentation, blister formation and destruction of the epidermis. SCD is characterized by chronic haemolysis, increased oxidative stress and decreased nitric oxide bioavailability, which promote ischaemia and inflammation and consequently impair vascular function in the skin. This cutaneous vasculopathy, coupled with venostasis around the ankle, creates an ideal environment for local vaso-occlusive crises, which can result in the development of leg ulcers that resemble arterial ulcers. Following the development of the ulcer, healing is hindered as a result of factors commonly observed in venous ulceration, including venous insufficiency, oedema and impaired angiogenesis. All of these factors are modulated by genetic factors. However, our current understanding of these genetic factors remains limited and does not yet enable us to accurately predict ulceration susceptibility.

Inflammatory status in pediatric sickle cell disease: Unravelling the role of immune cell subsets

Introduction: The mutation of the beta-globin gene that causes sickle cell disease (SCD) results in pleiotropic effects, such as hemolysis and vaso-occlusive crisis that can induce inflammatory mechanisms with deleterious consequences on the organism. Moreover, SCD patients display an increased susceptibility to infections. Few studies are currently available that evaluate a wide immunological profile in a pediatric population. This study proposes an evaluation of the immune profile in subjects with SCD in a pediatric population through a detailed analysis by flow cytometry. Methods and Materials: Peripheral blood samples from 53 pediatric patients with SCD (mean age 9.8 years, interquartile range 9 years) were obtained and then analyzed by flow cytometry, in order to evaluate changes in the immune populations compared to 40 healthy donors (mean age 7.3 years, interquartile range 9.5 years). Results: Our data showed an increase in neutrophils (with a reduction in the CD62L + subpopulation) and monocytes (with a decrease in HLA-DRlow monocytes) with normal values of lymphocytes in SCD patients. In the lymphocyte subpopulations analysis we observed lower values of CD4⁺ T cells (with higher number of memory and central memory T lymphocytes) with increased frequency of CD8⁺ T cells (with a predominant naive pattern). Moreover, we observed higher values of CD39⁺ Tregs and lower HLA-DR+ and CD39^- T cells with an increased Th17, Th1-17 and Th2 response. Conclusion: We observed immunological alterations typical of an inflammatory status (increase in activated neutrophils and monocytes) associated with a peculiar Treg pattern (probably linked to a body attempt to minimize inflammation intrinsic to SCD). Furthermore, we highlighted a T helper pathway associated with inflammation in line with other studies. Our data showed that immunological markers may have an important role in the understanding the pathophysiology of SCD and in optimizing targeted therapeutic strategies for each patient.

Regulatory T-cell phenotypes in children with sickle cell disease

BACKGROUND

Regulatory T cells (Tregs) are linked to a reduction in alloreactive immune responses, but few studies have investigated the impact of hydroxyurea (HU) therapy on Tregs in sickle cell disease (SCD).

METHODS

Our case-controlled study presented here included two groups, the first comprising 60 pediatric SCD patients, 30 of whom did not receive any treatment and 30 who received HU, and the second group consisting of 30 healthy controls. Flow cytometry was used to evaluate the percentage of CD4⁺CD25^+highFoxp3⁺ Tregs present and their phenotypes.

RESULTS

The percentage of CD4⁺CD25^+high Tregs was significantly increased in untreated SCD patients in comparison to treated SCD patients and controls. Conversely, treated SCD children had a lower percentage of CD4⁺CD25^+high Tregs than controls. In addition, a significant increase in the percentage of CD4⁺CD25^+highFoxp3⁺ Tregs was found in untreated SCD patients, compared to in HU-treated patients and controls. The percentage of naive CD45RA⁺ Tregs was significantly decreased in untreated SCD patients when compared to other groups.

CONCLUSIONS

Among children with SCD, HU treatment exhibited significant qualitative and quantitative effects on Tregs by decreasing their frequency, and increasing the proportion of naive CD45RA⁺ Tregs and reducing levels of the most suppressive Tregs: HLA-DR⁺, CD39⁺, and CD69⁺.

IMPACT

Among children with, SCD, HU treatment exhibited significant qualitative and quantitative effects on Tregs. HU treatment in SCD decreases the frequency of Tregs, as well as the levels of the most suppressive Tregs: HLA-DR⁺, CD39⁺, and CD69⁺. At the same time, HU increases the proportion of naive CD45RA⁺ Tregs. Our study showed the impact of HU therapy on Tregs in children with SCD.

Anti-inflammatory cytokines in sickle cell disease

Sickle cell disease (SCD) is a well-studied monogenetic disease with an established chronic inflammatory component. The paradigm shift towards inflammation has made the pathophysiology of SCD even more complex. Studies have shown that an imbalance between the pro-inflammatory and anti-inflammatory cytokines in SCD exists; however, the reports are skewed toward the pro-inflammatory mediators. We enumerate recent in vitro and in vivo studies on anti-inflammatory cytokines in SCD patients, and discuss the biology of anti-inflammatory cytokines including the already reported IL-2, TGF-β, and IL-10 as well as the recently discovered IL-27, IL-35 and IL-37. This review will improve the understanding of the pathophysiology of SCD and aid in the search of new therapeutic options for patients with SCD.

Common, But Neglected: A Comprehensive Review of Leg Ulcers in Sickle Cell Disease

OBJECTIVE

To compile available evidence to better understand the management of leg ulcers in sickle cell disease (SCD), as well as describe potential therapeutic steps that may be required to improve the quality of life of patients with SCD leg ulcers.

DATA SOURCES

MEDLINE, PubMed, EMBASE, and Web of Science databases.

STUDY SELECTION

A comprehensive search was conducted to retrieve relevant studies using the keywords "sickle cell disease and leg ulcer," "ulcer treatments, diagnosis and sickle cell," and "wound sickle cell." Studies published through July 2020 were included.

DATA EXTRACTION

Two independent authors selected all studies that assessed the relationship between leg ulcer and SCD identified from online databases.

DATA SYNTHESIS

The authors have summarized updated information on pathophysiology (vasculopathy linked to chronic hemolysis and endothelial dysfunction), diagnosis, and available treatment options to unravel the dermohematologic connection between leg ulcers and SCD.

CONCLUSIONS

It is the authors' hope that this detailed discussion of the information available on leg ulcers and SCD will lead to a better appreciation of this clinical problem by the clinicians and researchers and in turn have a long-term positive effect on the quality of life of patients with SCD. Researchers should design new trials considering these insights and potential therapeutic approaches based on current knowledge.

CD4+ T Cell Profile and Activation Response in Sickle Cell Disease Patients with Osteonecrosis

Recent evidence suggests that abnormalities involving CD4⁺T lymphocytes are associated with the pathophysiology of osteonecrosis (ON); however, few studies have addressed the CD4⁺T cells in ON related to sickle cell disease (SCD/ON). In addition, T cells producing multiple cytokines simultaneously are often present in the inflammatory milieu and may be implicated in the immune response observed in SCD/ON. In the present study, we aimed to characterize the functional status of CD4⁺T cells in SCD by simultaneously determining the frequency of IFN-γ ⁺, IL-4⁺, and IL-17⁺ CD4⁺T in cell cultures under exogenous stimuli. Peripheral blood mononuclear cells (PB-MNCs) from 9 steady-state SCD patients, 15 SCD/ON patients, and 19 healthy controls had functional status of CD4⁺T cells analyzed. Bone marrow mononuclear cells (BM-MNCs) from 24 SCD/ON patients (SCD BM) and 18 patients with ON not related to SCD (non-SCD BM) were also analyzed. We found that PB-MNC of SCD patients with or without ON presented significantly reduced TCD4⁺, TCD8⁺, and TCD4⁺ naïve cell frequencies and increased frequency of circulating CD4⁺T cells able to simultaneously produce IFN-γ ⁺/IL4⁺ and IL-17⁺/IL4⁺ compared to healthy controls. Conversely, the polyclonal stimulation of BM-MNC induced an increased frequency of CD4⁺IFN-γ ⁺ and CD4⁺IL-17⁺ in SCD BM compared to non-SCD BM. The increased proportion of CD4⁺ T cells able to produce a broad spectrum of proinflammatory cytokines after a strong stimulus indicates that the immune system in SCD/ON patients presents an expressive pool of partially differentiated cells ready to take on effector function. It is possible that this increased subpopulation may extend to inflammatory sites of target organs and may contribute to the maintenance of inflammation and the pathophysiology of osteonecrosis in sickle cell disease.

Immune mechanisms involved in sickle cell disease pathogenesis: current knowledge and perspectives

Sickle cell disease (SCD) is caused by a single point mutation in the β-chain of the hemoglobin gene that results in the replacement of glutamic acid with valine in the hemoglobin protein. However, recent studies have demonstrated that alterations in several other genes, especially immune related genes, may be associated with complications of SCD. In fact, higher chronic inflammatory status is related to more severe clinical symptoms in SCD patients, suggesting crucial roles of the immune system in SCD physiopathology. Nevertheless, although participation of innate immune cells in SCD pathogenesis has been broadly and extensively described, little is known about the roles of the adaptive immune system in this disease. In addition, the influence of treatments on the immune system of SCD patients and their complications (such as alloimmunization) are not yet completely understood. Thus, we reviewed the current knowledge about the immune mechanisms involved in SCD pathogenesis. We suggest recommendations for future studies to allow for a broader understanding of SCD pathogenesis, helping in the development of new therapies and improvement in the life quality and expectancy of patients.

Sickle Cell Anemia Patients Display an Intricate Cellular and Serum Biomarker Network Highlighted by TCD4+CD69+ Lymphocytes, IL-17/MIP-1β, IL-12/VEGF, and IL-10/IP-10 Axis

BACKGROUND

Sickle cell anemia (SCA) is associated with a chronic proinflammatory state characterized by elevated leukocyte count, mortality from severe recurrent infections, and subsequent vasoocclusive complications with leukocyte adhesion to the endothelium and increased plasma levels of inflammatory cytokines. The immune system has a close connection with morbidity in SCA, but further studies are needed to uncover the involvement of innate and adaptive immunities in modulating the SCA physiopathology. We performed measurements of the frequency of innate and adaptive immunity cells, cytokines, chemokines, and growth factors and immunophenotyping of Toll-like receptor and adhesion molecule expression in the blood of SCA patients and healthy donors to evaluate the different profiles of these biomarkers, the relationship among them, and their correlation to laboratory records and death risk. Material and Methods. Immunophenotyping of cells, Toll-like receptors, and adhesion molecules were performed from peripheral blood samples of SCA patients and healthy donors by flow cytometry and cytokine/chemokine/growth factor measurement by the Luminex technique performed from the serum of the same subjects.

RESULTS

Cells of adaptive immunity such as IL-12, IL-17, and IL-10 cytokines; IL-8, IP-10, MIP-1α, MIP-1β, and RANTES chemokines; and VEGF, FGF-basic, and GM-CSF growth factors were higher in SCA patients than healthy donors regardless of any laboratorial and clinical condition. However, high death risk appears to have relevant biomarkers.

CONCLUSION

In the SCA pathophysiology at steady state, there is a broad immunological biomarker crosstalk highlighted by TCD4+CD69+ lymphocytes, IL-12 and IL-17 inflammatory and IL-10 regulatory cytokines, MIP-1α, MIP-1β, and IP-10 chemokines, and VEGF growth factor. High expression of TLR2 in monocytes and VLA-4 in TCD8+ lymphocytes and high levels of MIP-1β and RANTES appear to be relevant in high death risk conditions. The high reticulocytosis and high death risk conditions present common correlations, and there seems to be a balance by the Th2 profile.

Vitamin D Deficiency and Its Association with Inflammatory Markers, Lipid Profile and Regulatory T-cells in Pediatric Sickle Cell Disease Patients

We investigated vitamin D deficiency in pediatric sickle cell disease patients and its association with selected bone, lipid and inflammatory parameters. The study included 64 patients (33 SS and 31 SB) and 21 carriers (AS). Blood was obtained to assess levels of vitamin D, WBC, CRP, Ca, P, ALP, PTH, triglyceride, total cholesterol, LDL, VLDL, HDL, IL-2, IL-12, TNF-α, IL-4, IL-6, IL-10 and regulatory T cells. The patients were grouped according to their genotype (SS, SB) and vitamin D status (low or normal). Carriers were also grouped as low or normal vitamin D. Laboratory findings were similar between low and normal Vit D groups in SS, SB and AS genotypes except a lower IL-12 in SB-low vitamin D compared SB-normal vitamin D group. Acute chest syndrome was more frequent in SS-low Vit D (63%) compared to SS-normal Vit D (25%), SB-low Vit D (21%) and SB-normal Vit D (33%) (P = 0.045). Both SS and SB with low vitamin D had higher VLDL (P = 0.006 and P = 0.022), TNF-α (P = 0.001) and regulatory T cells (P = 0.000) compared to AS-low vitamin D. Both SS and SB with normal vitamin D had higher levels of regulatory T cells (P = 0.000) compared to AS-normal vitamin D. Vit D was not a modifier of selected inflammation, bone and lipid parameters in sickle cell disease. Acute chest syndrome was comparably more frequent in SS-low vitamin D. Increase of regulatory T cells in the patients was a result of chronic inflammation in sickle cell disease.

Increased CD4+CD45RA-FoxP3low cells alter the balance between Treg and Th17 cells in colitis mice

AIM

To investigate the role of regulatory T cell (Treg) subsets in the balance between Treg and T helper 17 (Th17) cells in various tissues from mice with dextran sulfate sodium-induced colitis.

METHODS

Treg cells, Treg cell subsets, Th17 cells, and CD4⁺CD25⁺FoxP3⁺IL-17⁺ cells from the lamina propria of colon (LPC) and other ulcerative colitis (UC) mouse tissues were evaluated by flow cytometry. Forkhead box protein 3 (FoxP3), interleukin 17A (IL-17A), and RORC mRNA levels were assessed by real-time PCR, while interleukin-10 (IL-10) and IL-17A levels were detected with a Cytometric Beads Array.

RESULTS

In peripheral blood monocytes (PBMC), mesenteric lymph node (MLN), lamina propria of jejunum (LPJ) and LPC from UC mice, Treg cell numbers were increased (P < 0.05), and FoxP3 and IL-10 mRNA levels were decreased. Th17 cell numbers were also increased in PBMC and LPC, as were IL-17A levels in PBMC, LPJ, and serum. The number of FrI subset cells (CD4⁺CD45RA⁺FoxP3^low) was increased in the spleen, MLN, LPJ, and LPC. FrII subset cells (CD4⁺CD45RA^-FoxP3^high) were decreased among PBMC, MLN, LPJ, and LPC, but the number of FrIII cells (CD4⁺CD45RA^-FoxP3^low) and CD4⁺CD25⁺FoxP3⁺IL-17A⁺ cells was increased. FoxP3 mRNA levels in CD4⁺CD45RA^-FoxP3^low cells decreased in PBMC, MLN, LPJ, and LPC in UC mice, while IL-17A and RORC mRNA increased. In UC mice the distribution of Treg, Th17 cells, CD4⁺CD45RA^-FoxP3^high, and CD4⁺CD45RA^-FoxP3^low cells was higher in LPC relative to other tissues.

CONCLUSION

Increased numbers of CD4⁺CD45RA^-FoxP3^low cells may cause an imbalance between Treg and Th17 cells that is mainly localized to the LPC rather than secondary lymphoid tissues.