Analysis of the Seasonal Fluctuation of γδ T Cells and Its Potential Relation with Vitamin D3

Intravital imaging of the human cornea reveals the differential effects of season on innate and adaptive immune cell morphodynamics

PURPOSE

While the external environment has been shown to shape the systemic human immune landscape, defining the in vivo immune status of peripheral tissues has remained a technical challenge. We recently developed functional in vivo confocal microscopy (Fun-IVCM) for dynamic, longitudinal imaging of corneal immune cells in living humans. This study investigated the effect of seasonal-driven environmental factors on the density, morphology and dynamic behavior of human corneal immune cell subsets.

DESIGN

Longitudinal, observational clinical study.

PARTICIPANTS

Sixteen healthy participants (18-40 years) attended two visits in distinct seasons in Melbourne, Australia (Visit 1: Spring/Summer: November-December 2021; Visit 2: Autumn/Winter: April-June 2022).

METHODS

Environmental data were collected over each period. Participants underwent ocular surface examinations and corneal Fun-IVCM (Heidelberg HRT-3, Rostock Corneal Module). Volume scans (80μm) were acquired at 5.5±1.5 minute intervals, for up to five timepoints. Time-lapse videos were created to analyze corneal immune cells, comprising epithelial T cells and dendritic cells (DCs), and stromal macrophages. Tear cytokines were analyzed using multiplex bead-based immunoassay.

MAIN OUTCOME MEASURES

Difference in the density, morphological and dynamic parameters of corneal immune cell subsets over the study periods.

RESULTS

Visit 1 was characterized by higher temperature, lower humidity, and higher air particulate and pollen levels than Visit 2. Clinical ocular surface parameters, and the density of immune cell subsets were similar across visits. At Visit 1 (Spring/Summer), corneal epithelial DCs were larger and more elongated, with a lower dendrite probing speed (0.38±0.21 vs 0.68±0.33μm/min, p<0.001) relative to Visit 2; stromal macrophages were more circular and had less dynamic activity (Visit 1: 7.2±1.9 vs Visit 2: 10.3±3.7 'dancing index', p<0.001). T cell morphology and dynamics were unchanged across periods. Basal tear levels of IL-2 and CXCL10 were lower during Spring/Summer.

CONCLUSION

This novel study shows that the in vivo morphodynamics of innate corneal immune cells (DCs, macrophages) are modified by environmental factors, but such effects are not evident for adaptive immune cells (T cells). The cornea is a potential non-invasive, in vivo 'window' to season-dependent changes to the human immune system, with capacity to yield new insight into environmental influences on immune regulation.

Development and Validation of Novel HPLC Methods for Quantitative Determination of Vitamin D3 in Tablet Dosage Form

In the present work, an efficient isocratic HPLC method was developed for the precise and accurate estimation of vitamin D3 in tablet form. The chromatographic conditions comprised an L3 silica column (5 µm in particle size, 4.6 mm × 250 mm) with a mobile phase n-hexane/ethyl acetate (85:15 v/v) with a flow rate of 2.0 mL/min and a detection wavelength of 292 nm. The new methodology was validated for accuracy, precision, specificity, robustness, and quantification limits according to an official monograph of USP/BP and ICH guidelines. The peak areas of the six replicates of the homogeneous sample were recorded. The mean value obtained was 67,301, and the relative standard deviation (RSD) was 0.1741. The linearity and range were in the acceptable bounds, i.e., 0.999, which was calculated using regression line analysis. The results show that the method is truly acceptable as the RSD, as the flow rate was 0.81%, while for the mobile phase composition, it was 0.72%, which lies in the acceptable range. The limit of detection (LOD) and the limit of quantification (LOQ) values were 0.0539 µg/mL and 0.1633 µg/mL, respectively. The % RSD of the intra and inter-day precision of the method was deemed acceptable according to the international commission for harmonization guidelines. The developed method has potential to be used for the detection and quantification of vitamin D3 during routine analysis for tablets in dosage form.

Empowering γδ T-cell functionality with vitamin C

Vitamin C (ascorbic acid) is a potent antioxidant and a cofactor for various enzymes including histone demethylases and methylcytosine dioxygenases. Vitamin C also exerts direct cytotoxicity toward selected tumor cells including colorectal carcinoma. Moreover, vitamin C has been shown to impact immune cell differentiation at various levels including maturation and/or functionality of T cells and their progenitors, dendritic cells, B cells, and NK cells. γδ T cells have recently attracted great interest as effector cells for cell-based cancer immunotherapy, due to their HLA-independent recognition of a large variety of tumor cells. While γδ T cells can thus be also applied as an allogeneic off-the-shelf product, it is obvious that the effector function of γδ T cells needs to be optimized to ensure the best possible clinical efficacy. Here we review the immunomodulatory mechanisms of vitamin C with a special focus on how vitamin C enhances the effector function of γδ T cells. We also discuss future directions of how vitamin C can be used in the clinical setting to boost the efficacy of adoptive cell therapies.

Low Vitamin D Levels Are Associated with Increased Cardiac Iron Uptake in Beta-Thalassemia Major

We evaluated the association of vitamin D and parathormone (PTH) levels with cardiac iron and function in beta-thalassemia major (β-TM) patients. Two-hundred and seventy-eight TM patients (39.04 ± 8.58 years, 56.8% females) underwent magnetic resonance imaging for the assessment of iron overload (T2* technique), biventricular function parameters (cine images), and replacement myocardial fibrosis (late gadolinium enhancement technique). Vitamin D levels were deficient (<20 ng/dL) in 107 (38.5%) patients, insufficient (20-30 ng/dL) in 96 (34.5%) patients, and sufficient (≥30 ng/dL) in 75 (27.0%) patients. Deficient vitamin D patients had a significantly higher frequency of myocardial iron overload (MIO; global heart T2* < 20 ms) than patients with sufficient and insufficient vitamin D levels and a significantly higher left ventricular end-diastolic volume index and mass index than patients with sufficient vitamin D levels. PTH was not associated with cardiac iron, function, or fibrosis. In the multivariate regression analysis, vitamin D, serum ferritin, and pancreatic iron levels were the strongest predictors of global heart T2* values. In receiver operating characteristic curve analysis, a vitamin D level ≤ 17.3 ng/dL predicted MIO with a sensitivity of 81.5% and a specificity of 75.3% (p < 0.0001). In TM, the periodic and regular assessment of vitamin D levels can be beneficial for the prevention of cardiac iron accumulation and subsequent overt dysfunction.

Hypovitaminosis D in persons with Down syndrome and autism spectrum disorder

BACKGROUND

Plasma levels of vitamin D have been reported to be low in persons with Down syndrome (DS) and existing data is limited to small and homogenous cohorts. This is of particular importance in persons with DS given the high rates of autoimmune disease in this population and the known relationship between vitamin D and immune function. This study sought to investigate vitamin D status in a multi-center cohort of individuals with DS and compare them to individuals with autism spectrum disorder (ASD) and neurotypical (NT) controls.

METHODS

A retrospective, multi-center review was performed. The three sites were located at latitudes of 42.361145, 37.44466, and 34.05349. Patients were identified by the International Classification of Diseases (ICD)-9 or ICD-10 codes for DS, ASD, or well-child check visits for NT individuals. The first vitamin D 25-OH level recorded in the electronic medical record (EMR) was used in this study as it was felt to be the most reflective of a natural and non-supplemented state. Vitamin D 25-OH levels below 30 ng/mL were considered deficient.

RESULTS

In total, 1624 individuals with DS, 5208 with ASD, and 30,775 NT controls were identified. Individuals with DS had the lowest mean level of vitamin D 25-OH at 20.67 ng/mL, compared to those with ASD (23.48 ng/mL) and NT controls (29.20 ng/mL) (p < 0.001, 95% CI: -8.97 to -6.44). A total of 399 (24.6%) individuals with DS were considered vitamin D deficient compared to 1472 (28.3%) with ASD and 12,397 (40.3%) NT controls (p < 0.001, 95% CI: -5.43 to -2.36). Individuals with DS with higher body mass index (BMI) were found to be more likely to have lower levels of vitamin D (p < 0.001, 95% CI: -0.3849 to -0.1509). Additionally, having both DS and a neurologic diagnosis increased the likelihood of having lower vitamin D levels (p < 0.001, 95% CI: -5.02 to -1.28). Individuals with DS and autoimmune disease were much more likely to have lower vitamin D levels (p < 0.001, 95% CI: -6.22 to -1.55). Similarly, a history of autoimmunity in a first-degree relative also increased the likelihood of having lower levels of vitamin D in persons with DS (p = 0.01, 95% CI: -2.45 to -0.63).

CONCLUSIONS

Individuals with DS were noted to have hypovitaminosis D in comparison to individuals with ASD and NT controls. Associations between vitamin D deficiency and high BMI, personal autoimmunity, and familial autoimmunity were present in individuals with DS.

1α,25(OH)2D3 ameliorates insulin resistance by alleviating γδ T cell inflammation via enhancing fructose-1,6-bisphosphatase 1 expression

Background: Chronic inflammation caused by immune cells is the central link between obesity and insulin resistance. Targeting the inflammatory process is a highly promising method for reversing systemic insulin resistance. Methods: Blood samples were prospectively collected from 68 patients with type 2 diabetes. C57BL/6J mice were fed either a high-fat diet (HFD) or normal chow (NC). We performed phenotypical and functional analyses of immune cells using flow cytometry. Vitamin D receptor (VDR) knockout γδ T cells were constructed using Cas9-gRNA targeted approaches to identify 1α,25(OH)2D3/VDR signaling pathway-mediated transcriptional regulation of fructose-1,6-bisphosphatase (FBP1) in γδ T cells. Results: Serum vitamin D deficiency aggravates inflammation in circulating γδ T cells in type 2 diabetes patients. We defined a critical role for 1α,25(OH)2D3 in regulating glycolysis metabolism, protecting against inflammation, and alleviating insulin resistance. Mechanistically, 1α,25(OH)2D3-VDR promoted FBP1 expression to suppress glycolysis in γδ T cells, thereby inhibiting Akt/p38 MAPK phosphorylation and reducing inflammatory cytokine production. Notably, therapeutic administration of 1α,25(OH)2D3 restrained inflammation in γδ T cells and ameliorated systemic insulin resistance in obese mice. Conclusions: Collectively, these findings show that 1α,25(OH)2D3 plays an important role in maintaining γδ T cell homeostasis by orchestrating metabolic programs, and is a highly promising target for preventing obesity, inflammation, and insulin resistance.

Reduced serum 25(OH)D is closely related to bronchial mucus plug formation in children with mycoplasma pneumonia: A prospective cohort study

Background

The relationship between vitamin D nutritional status and the formation of bronchial mucus plugs (BMPs) is unclear. The aims of the current study were to investigate associations between serum 25(OH)D levels, serum inflammatory factors, and clinical characteristics in children with mycoplasma pneumonia (MPP), and to summarize the risk factors for BMPs in children with MPP.

Methods

Clinical data from 175 children with MPP were collected and analyzed, the children were divided into a BMP group and a non-BMP group. Serum 25(OH)D levels, IL-8, and various inflammatory factors were compared in the two groups. Associations between 25(OH)D levels and IL-8, various inflammatory factors, and clinical characteristics were analyzed, and the diagnostic value of serum 25(OH)D levels was assessed.

Results

Serum 25(OH)D level was significantly lower in the BMP group (p < 0.05). Serum IL-8 level, percentages of neutrophils, and some inflammatory factors were significantly higher in the BMP group (p < 0.05). Serum 25(OH)D level was negatively correlated with IL-8, neutrophil percentage, various inflammatory factors (all p < 0.05). It was also associated with lobular infection, pleural effusion, mechanical ventilation, and mycoplasma 2,063/2,064 mutation (all p < 0.05). In multivariate regression analysis 25(OH)D [odds ratio (OR) 0.98, 95% confidence interval (CI) 0.97-0.99, p = 0.003], IL-8 (OR 1.02, 95% CI 1.00-1.04, p = 0.002), polylobular infection (OR 1.75, 95% CI 1.17-2.64, p = 0.007), and MP DNA copies (OR 0.98, 95% CI 1.04-1.01, p = 0.022) were independent risk factors for BMPs, and the area under the curve value was 0.915 (95% CI 0.895-0.935). If the serum 25(OH)D level was <50 nmol/L, the respective percentages for sensitivity, specificity, positive predictive value, and negative predictive value were 97, 81, 78.9, and 97.6%.

Conclusions

Vitamin D deficiency is common in children with MPP, and 25(OH)D levels are closely associated with inflammatory factors and disease severity in children. The serum 25 (OH) D level of MPP children with BMPs was lower than that of children without BMPs. Serum 25(OH)D can be used as a marker for the diagnosis of MPP in children with BMPs.

The multisensory regulation of unconventional T cell homeostasis

Unconventional T cells typically group γδ T cells, invariant Natural Killer T cells (NKT) and Mucosal Associated Invariant T (MAIT) cells. With their pre-activated status and biased tropism for non-lymphoid organs, they provide a rapid (innate-like) and efficient first line of defense against pathogens at strategical barrier sites, while they can also trigger chronic inflammation, and unexpectedly contribute to steady state physiology. Thus, a tight control of their homeostasis is critical to maintain tissue integrity. In this review, we discuss the recent advances of our understanding of the factors, from neuroimmune to inflammatory regulators, shaping the size and functional properties of unconventional T cell subsets in non-lymphoid organs. We present a general overview of the mechanisms common to these populations, while also acknowledging specific aspects of their diversity. We mainly focus on their maintenance at steady state and upon inflammation, highlighting some key unresolved issues and raising upcoming technical, fundamental and translational challenges.