Vitamin D receptor signals regulate effector and memory CD8 T cell responses to infections in mice

Correlation Between Vitamin D Status and HBsAg Antibody Levels in Indonesian Adolescents Immunised Against Hepatitis B

Introduction

Hepatitis B virus (HBV) infection is a global health problem. Anti-hepatitis B surface antigen (HBsAg) levels increase along with vitamin D levels in adults. However, few studies have examined this relationship in adolescents. Few studies have examined the relationship between vitamin D and HBsAg antibody levels, especially in Indonesia.

Methods

This cross-sectional study examined vitamin D and anti-HBsAg levels before and after hepatitis B immunisation. All subjects blood was taken to check for vitamin D level. This study was part of the Safety and Preliminary of Immunogenicity Following Recombinant Hepatitis B (Bio Farma) Vaccine in Adults and Children Phase I trial.

Results

This study found that 25-hydroxyvitamin D [25(OH)D] status was primarily deficient based on endocrine criteria. The children's hepatitis B antibody response was mostly <10 mIU/mL before and ≥10 mIU/mL after vaccination. There was a relationship between sex and 25(OH)D status, with median 25(OH)D levels higher in females (18.2 ng/mL) than in males (9.8 ng/mL). However, the relationship between vitamin 25(OH)D status and anti-HBsAg levels pre- and post-vaccination was not significant.

Discussion

However, some research found that vitamin D supplementation after immunisation did not impact vaccine response, several studies have reported that vitamin D can decrease HBV replication through various mechanisms, including reducing viral transcription and interfering with viral protein synthesis.

Conclusion

There was no relationship between 25(OH)D status and anti-HBsAg levels. Further research is needed to elucidate the underlying mechanisms and establish optimal treatment strategies.

Case-control study of serum vitamin D concentrations in hospitalised patients with COVID-19 and hospitalised controls suffering with respiratory tract infections of differing aetiology

This study explored the prevalence of low serum vitamin D in patients admitted with acute respiratory tract infections (ARTIs) such as COVID-19. This study investigated whether patients with COVID-19 had lower serum vitamin D compared with patients with ARTIs of other aetiology. A case-control study was performed with cases of COVID-19 and controls of non-COVID-19 ARTIs. Patients were enrolled from a single general medical ward in a secondary care hospital between 15 April 2020 and 15 May 2020. Exclusion criteria were an oxygen requirement of >8 L/min. Data collected included serum 25-hydroxyvitamin D concentration, venous plasma glucose concentration and heamoglobin A1c. Outcomes measured were length of hospital stay, deaths, the need for high dependency and intensive care unit involvement. A total of 60 patients of five ethnic groups were enrolled, 85% (n=46) were of White-British ethnicity. The data analysis is based on these 46 patients of which 24 were non-COVID-19 patients with ARTI and 22 were patients with COVID-19. Overall, 80% of the study population had a serum vitamin D concentration below 50 nmol/L with median concentrations of 30 nmol/L and 35 nmol/L for patients with COVID-19 and non-COVID-19 ARTIs respectively. A Mann-Whitney sign-ranked test with respect to serum vitamin D concentration found no statistically significant difference between cases and controls, p=0.09. There was no significant difference in the length of stay, body mass index and rates of various comorbidities such as diabetes mellitus (DM), hypertension and lung disease in both study groups. However, DM was found to be associated with lower serum vitamin D concentrations. The results of this study support published literature showing an association between low serum vitamin D and ARTIs including COVID-19. However, this study did not identify patients with COVID-19 to have a statistically significant lower serum vitamin D concentration than non-COVID-19 patients with ARTI.

Changes in the immune response against SARS-CoV-2 in individuals with severe COVID-19 treated with high dose of vitamin D

Main cause of severe illness and death in COVID-19 patients appears to be an excessive but ineffectual inflammatory immune response that may cause severe acute respiratory distress syndrome (ARDS). Vitamin D may favour an anti-inflammatory environment and improve cytotoxic response against some infectious diseases. A multicenter, single-blind, prospective, randomized clinical trial was approved in patients with COVID-19 pneumonia and levels of 25-hydroxyvitamin D (25(OH)D) of 14.8 ng/ml (SD: 6.18) to test antiviral efficacy, tolerance and safety of 10,000 IU/day of cholecalciferol (vitamin D3) for 14 days, in comparison with 2000 IU/day. After supplementation, mean serum 25(OH)D levels increased to 19 ng/ml on average in 2000 IU/day versus 29 ng/ml in 10,000 IU/day group (p < 0.0001). Although levels of inflammatory cytokines were not modified by treatment with 10,000 IU/day, there was an increase of anti-inflammatory cytokine IL-10 and higher levels of CD4+ T cells, with predominance of T central memory subpopulation. Cytotoxic response against pseudotyped SARS-CoV-2 infected cells was increased more than 4-fold in patients who received 10,000 IU/day. Moreover, levels of IFNγ were significantly higher in this group. Beneficial effect of supplementation with 10,000 IU/day was also observed in participants who developed ARDS and stayed at the hospital for 8.0 days, whereas those who received 2000 IU/day stayed for 29.2 days (p = 0.0381). Administration of high doses of vitamin D3 as adjuvant of the standard care treatment during hospitalization for COVID-19 may improve the inflammatory environment and cytotoxic response against pseudotyped SARS-CoV-2 infected cells, shortening the hospital stay and, possibly, improving the prognosis.

Effects of repeated infections with non-typeable Haemophilus influenzae on lung in vitamin D deficient and smoking mice

Background

In chronic obstructive pulmonary disease (COPD), exacerbations cause acute inflammatory flare-ups and increase the risk for hospitalization and mortality. Exacerbations are common in all disease stages and are often caused by bacterial infections e.g., non-typeable Heamophilus influenzae (NTHi). Accumulating evidence also associates vitamin D deficiency with the severity of COPD and exacerbation frequency. However, it is still unclear whether vitamin D deficiency when combined with cigarette smoking would worsen and prolong exacerbations caused by repeated infections with the same bacterial strain.

Methods

Vitamin D sufficient (VDS) and deficient (VDD) mice were exposed to nose-only cigarette smoke (CS) for 14 weeks and oropharyngeally instilled with NTHi at week 6, 10 and 14. Three days after the last instillation, mice were assessed for lung function, tissue remodeling, inflammation and immunity. The impact of VDD and CS on inflammatory cells and immunoglobulin (Ig) production was also assessed in non-infected animals while serum Ig production against NTHi and dsDNA was measured in COPD patients before and 1 year after supplementation with Vitamin D3.

Results

VDD enhanced NTHi eradication, independently of CS and complete eradication was reflected by decreased anti-NTHi Ig’s within the lung. In addition, VDD led to an increase in total lung capacity (TLC), lung compliance (Cchord), MMP12/TIMP1 ratio with a rise in serum Ig titers and anti-dsDNA Ig’s. Interestingly, in non-infected animals, VDD exacerbated the CS-induced anti-NTHi Ig’s, anti-dsDNA Ig’s and inflammatory cells within the lung. In COPD patients, serum Ig production was not affected by vitamin D status but anti-NTHi IgG increased after vitamin D3 supplementation in patients who were Vitamin D insufficient before treatment.

Conclusion

During repeated infections, VDD facilitated NTHi eradication and resolution of local lung inflammation through production of anti-NTHi Ig, independently of CS whilst it also promoted autoantibodies. In COPD patients, vitamin D supplementation could be protective against NTHi infections in vitamin D insufficient patients. Future research is needed to decipher the determinants of dual effects of VDD on adaptive immunity.

Trail registration

ClinicalTrials, NCT00666367. Registered 23 April 2008, https://www.clinicaltrials.gov/ct2/show/study/NCT00666367.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-01962-6.

Pharmacological Modulation of Immune Responses by Nutritional Components

The incidence of noncommunicable diseases (NCDs) has increased over the last few decades, and one of the major contributors to this is lifestyle, especially diet. High intake of saturated fatty acids and low intake of dietary fiber is linked to an increase in NCDs. Conversely, a low intake of saturated fatty acids and a high intake of dietary fiber seem to have a protective effect on general health. Several mechanisms have been identified that underlie this phenomenon. In this review, we focus on pharmacological receptors, including the aryl hydrocarbon receptor, binding partners of the retinoid X receptor, G-coupled protein receptors, and toll-like receptors, which can be activated by nutritional components and their metabolites. Depending on the nutritional component and the receptors involved, both proinflammatory and anti-inflammatory effects occur, leading to an altered immune response. These insights may provide opportunities for the prevention and treatment of NCDs and their inherent (sub)chronic inflammation. SIGNIFICANCE STATEMENT: This review summarizes the reported effects of nutritional components and their metabolites on the immune system through manipulation of specific (pharmacological) receptors, including the aryl hydrocarbon receptor, binding partners of the retinoid X receptor, G-coupled protein receptors, and toll-like receptors. Nutritional components, such as vitamins, fibers, and unsaturated fatty acids are able to resolve inflammation, whereas saturated fatty acids tend to exhibit proinflammatory effects. This may aid decision makers and scientists in developing strategies to decrease the incidence of noncommunicable diseases.

Role of vitamin D in regulating COVID-19 severity-An immunological perspective

Vitamin D, a key nutrient/prohormone classically associated with skeletal health, is also an important immunomodulator, with pleotropic effects on innate and adaptive immune cells. Outcomes of several chronic, autoimmune, and infectious diseases are linked to vitamin D. Emergent correlations of vitamin D insufficiency with coronavirus-induced disease 2019 (COVID-19) severity, alongside empirical and clinical evidence of immunoregulation by vitamin D in other pulmonary diseases, have prompted proposals of vitamin D supplementation to curb the COVID-19 public health toll. In this review paper, we engage an immunological lens to discuss potential mechanisms by which vitamin D signals might regulate respiratory disease severity in severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infections, vis a vis other pulmonary infections. It is proposed that vitamin D signals temper lung inflammatory cascades during SARS-CoV2 infection, and insufficiency of vitamin D causes increased inflammatory cytokine storm, thus leading to exacerbated respiratory disease. Additionally, analogous to studies of reduced cancer incidence, the dosage of vitamin D compounds administered to patients near the upper limit of safety may serve to maximize immune health benefits and mitigate inflammation and disease severity in SARS-CoV2 infections. We further deliberate on the importance of statistically powered clinical correlative and interventional studies, and the need for in-depth basic research into vitamin D-dependent host determinants of respiratory disease severity.

Vitamin D in respiratory viral infections: a key immune modulator?

Respiratory viral infections are common respiratory diseases. Influenza viruses, RSV and SARS-COV2 have the potential to cause severe respiratory infections. Numerous studies have shown that unregulated immune response to these viruses can cause excessive inflammation and tissue damage. Therefore, regulating the antiviral immune response in the respiratory tract is of importance. In this regard, recent years studies have emphasized the importance of vitamin D in respiratory viral infections. Although, the most well-known role of vitamin D is to regulate the metabolism of phosphorus and calcium, it has been shown that this vitamin has other important functions. One of these functions is immune regulation. Vitamin D can regulate the antiviral immune response in the respiratory tract in order to provide an effective defense against respiratory viral infections and prevention from excessive inflammatory response and tissue damage. In addition, this vitamin has preventive effects against respiratory viral infections. Some studies during the COVID-19 pandemic have shown that vitamin D deficiency may be associated with a higher risk of mortality and sever disease in patients with COVID-19. Since, more attention has recently been focused on vitamin D. In this article, after a brief overview of the antiviral immune response in the respiratory system, we will review the role of vitamin D in regulating the antiviral immune response comprehensively. Then we will discuss the importance of this vitamin in influenza, RSV, and COVID-19.

Efeitos contrastantes da vitamina D sobre a resposta imune inata e adquirida e seu impacto na recuperação da tuberculose

A vitamina D é um hormônio essencial para o organismo, podendo ser obtida da dieta ou, principalmente, gerada pela pele após exposição à luz solar ultravioleta B. Na sua forma ativa (1,25(OH)2D) ela controla a absorção de cálcio e fósforo do intestino para a corrente sanguínea e participa de diversos processos celulares e fisiológicos. A ligação da 1,25(OH)2D ao receptor da vitamina D (VDR) presente em diversas células, como as células do sistema imunológico, induz a transcrição de genes que podem, por exemplo, modular a resposta imune inata e adquirida. A deficiência de vitamina D ou do VDR é associada a problemas de saúde como desordens esqueléticas, hipertensão, doenças cardiovasculares, diabetes mellitus, dislipidemias, doenças autoimunes e doenças infecciosas. Neste sentido, a suplementação com vitamina D tem sido proposta como uma possível medida preventiva, podendo ser aplicada em muitas patologias, em especial na tuberculose. Principal causa de morte por um único agente infeccioso, a tuberculose é responsável por cerca de 1,3 milhões de óbitos por ano no mundo. Publicações recentes apontam efeitos diversos da vitamina D na resposta imune inata e adquirida. A 1,25(OH)2D3 na presença do interferon (IFN)-γ é capaz de aumentar a atividade bactericida do macrófago contra o M. tuberculosis, aumentando a produção de peptídios antimicrobianos e estimulando a autofagia, favorecendo assim a lise de bacilos localizados em fagossomos. Por outro lado, a vitamina D em linfócitos T mostra efeito tolerogênico que favorece o controle de respostas inflamatórias excessivas. Neste trabalho de revisão são apresentados estudos recentes envolvendo efeitos da vitamina D na resposta imune inata e adquirida. Além disso, considerações sobre deficiência de vitamina D e maior risco de contrair tuberculose, e efeitos contrastantes da suplementação com vitamina D na prevenção e tratamento da TB, são discutidos.

Repurposing vitamin D for treatment of human malignancies via targeting tumor microenvironment

Tumor cells along with a small proportion of cancer stem cells exist in a stromal microenvironment consisting of vasculature, cancer-associated fibroblasts, immune cells and extracellular components. Recent epidemiological and clinical studies strongly support that vitamin D supplementation is associated with reduced cancer risk and favorable prognosis. Experimental results suggest that vitamin D not only suppresses cancer cells, but also regulates tumor microenvironment to facilitate tumor repression. In this review, we have outlined the current knowledge on epidemiological studies and clinical trials of vitamin D. Notably, we summarized and discussed the anticancer action of vitamin D in cancer cells, cancer stem cells and stroma cells in tumor microenvironment, providing a better understanding of the role of vitamin D in cancer. We presently re-propose vitamin D to be a novel and economical anticancer agent.

Differential effect of dietary vitamin D supplementation on natural killer cell activity in lean and obese mice

Vitamin D has an immunoregulatory effect on both innate and adaptive immunity. Contradictory results regarding vitamin D and natural killer (NK) cell functions have been reported with in vitro studies, but little is known about this in vivo. We investigated whether vitamin D levels (50, 1000 or 10,000 IU/kg of diet: DD, DC or DS) affect NK cell functions in mice fed a control or high-fat diet (10% or 45% kcal fat: CD or HFD) for 12 weeks. The splenic NK cell activity was significantly higher in the CD-DS group than the HFD-DS group, and the CD-DS group showed significantly higher NK cell activity compared with the CD-DD and CD-DC groups. However, no difference in NK cell activity was observed among the HFD groups fed different levels of vitamin D. The splenic population of NK cells was significantly higher in the CD-DS group than the HFD-DS group. There was no difference in the intracellular expression of IFN-γ and the surface expression of NKG2D and CD107a in NK cells by both dietary fat and vitamin D content. The splenic mRNA expression of Ifng and Ccl5 was significantly lower in the HFD groups compared with the CD groups, but there was no difference in the mRNA levels of Vdup1 and Vdr among the groups. Taken together, these results suggest that dietary vitamin D supplementation can modulate innate immunity by increasing NK activity in control mice but not in obese mice. This effect might be mediated through alternation of the splenic NK cell population.

The role of vitamin D on circulating memory T cells in children: The Generation R study

BACKGROUND

Previous studies have demonstrated that vitamin D affects T-cell function and maturation via the vitamin D receptor. However, no studies in children have been performed on this topic. Because most of the T-cell memory is formed in the first 5 years of life, we aimed to determine the association between serum 25-hydroxyvitamin D (25(OH)D) levels and numbers of circulatory naive, central memory (Tcm), and effector memory (Tem) T lymphocytes in a large population of healthy children.

METHODS

Among 3189 children participating in a population-based prospective cohort, we measured 25(OH)D levels and performed detailed immunophenotyping of naive and memory T lymphocytes at a median age of 6.0 years (95% range 5.7-7.9). Detailed lymphocyte subsets were available in 986 children. Multivariable linear regression analyses were performed to determine the association between 25(OH)D and the maturation of T lymphocytes in children adjusted for cord blood 25(OH)D levels, herpes seropositivity, sociodemographic and lifestyle confounders. Furthermore, multivariable logistic regression analyses were performed to determine associations between 25(OH)D and childhood infections.

RESULTS

Higher 25(OH)D levels were associated with higher numbers of Tem lymphocytes. Every 10 nmol/L higher 25(OH)D was associated with 2.20% (95% CI 0.54-3.89; P=.009) higher CD4TemRA, 1.50% (95% CI 0.38-2.62; P=.008) higher CD4TemRO, and 1.82% (95% CI 0.11-3.56; P=.037) higher CD8TemRA cell numbers. Generally, stronger associations were observed among boys. 25(OH)D levels were not significantly associated with naive, Tcm cell numbers, herpes seropositivity, or URTIs.

CONCLUSIONS

Our results suggest that vitamin D enhances cellular immunity in young children.

Vitamin D-Regulated MicroRNAs: Are They Protective Factors against Dengue Virus Infection?

Over the last few years, an increasing body of evidence has highlighted the critical participation of vitamin D in the regulation of proinflammatory responses and protection against many infectious pathogens, including viruses. The activity of vitamin D is associated with microRNAs, which are fine tuners of immune activation pathways and provide novel mechanisms to avoid the damage that arises from excessive inflammatory responses. Severe symptoms of an ongoing dengue virus infection and disease are strongly related to highly altered production of proinflammatory mediators, suggesting impairment in homeostatic mechanisms that control the host's immune response. Here, we discuss the possible implications of emerging studies anticipating the biological effects of vitamin D and microRNAs during the inflammatory response, and we attempt to extrapolate these findings to dengue virus infection and to their potential use for disease management strategies.

Vitamin D Control of Hematopoietic Cell Differentiation and Leukemia

It is now well known that in the mammalian body vitamin D is converted by successive hydroxylations to 1,25-dihydroxyvitamin D (1,25D), a steroid-like hormone with pleiotropic properties. These include important contributions to the control of cell proliferation, survival and differentiation, as well as the regulation of immune responses in disease. Here, we present recent advances in current understanding of the role of 1,25D in myelopoiesis and lymphopoiesis, and the potential of 1,25D and analogs (vitamin D derivatives; VDDs) for the control of hematopoietic malignancies. The reasons for the unimpressive results of most clinical studies of the therapeutic effects of VDDs in leukemia and related diseases may include the lack of a precise rationale for the conduct of these studies. Further, clinical trials to date have generally used extremely heterogeneous patient populations and, in many cases, small numbers of patients, generally without controls. Although low calcemic VDDs have been used and combined with agents that can increase the leukemia cell killing or differentiation effects in acute leukemias, the sequencing of agents used for combination therapy should to be more clearly delineated. Most importantly, it is recommended that in future clinical trials the rationale for the basis of the enhancing action of drug combinations should be clearly articulated and the effects on anticancer immunity should also be evaluated.

1α,25(OH)2 Vitamin D3 Modulates Avian T Lymphocyte Functions without Inducing CTL Unresponsiveness

1,25-Dihydroxyvitamin D3 (Vitamin D) is a naturally synthesized fat soluble vitamin shown to have immunomodulatory, anti-inflammatory and cancer prevention properties in human and murine models. Here, we studied the effects of Vitamin D on the functional abilities of avian T lymphocytes using chicken Interferon (IFN)-γ ELISPOT assay, BrdU proliferation assay, Annexin V apoptosis assay and PhosFlow for detecting phosphorylated signalling molecules. The results demonstrate that Vitamin D significantly inhibited the abilities of T lymphocytes to produce IFN-γ and proliferate in vitro (P≤0.05), but retained their ability to undergo degranulation, which is a maker for cytotoxicity of these cells. Similarly, Vitamin D did not inhibit Extracellular signal-Regulated Kinase (ERK) 1/2 phosphorylation, a key mediator in T cell signalling, in the stimulated T lymphocytes population, while reduced ERK1/2 phosphorylation levels in the unstimulated cells. Our data provide evidence that Vitamin D has immuno-modulatory properties on chicken T lymphocytes without inducing unresponsiveness and by limiting immuno-pathology can promote protective immunity against infectious diseases of poultry.

Role of vitamin D in cytotoxic T lymphocyte immunity to pathogens and cancer

The discovery of vitamin D receptor (VDR) expression in immune cells has opened up a new area of research into immunoregulation by vitamin D, a niche that is distinct from its classical role in skeletal health. Today, about three decades since this discovery, numerous cellular and molecular targets of vitamin D in the immune system have been delineated. Moreover, strong clinical associations between vitamin D status and the incidence/severity of many immune-regulated disorders (e.g. infectious diseases, cancers and autoimmunity) have prompted the idea of using vitamin D supplementation to manipulate disease outcome. While much is known about the effects of vitamin D on innate immune responses and helper T (T(H)) cell immunity, there has been relatively limited progress on the frontier of cytotoxic T lymphocyte (CTL) immunity--an arm of host cellular adaptive immunity that is crucial for the control of such intracellular pathogens as human immunodeficiency virus (HIV), tuberculosis (TB), malaria, and hepatitis C virus (HCV). In this review, we discuss the strong historical and clinical link between vitamin D and infectious diseases that involves cytotoxic T lymphocyte (CTL) immunity, present our current understanding as well as critical knowledge gaps in the realm of vitamin D regulation of host CTL responses, and highlight potential regulatory connections between vitamin D and effector and memory CD8 T cell differentiation events during infections.

Vitamin D every day to keep the infection away?

Within the last decade, vitamin D has emerged as a central regulator of host defense against infections. In this regard, vitamin D triggers effective antimicrobial pathways against bacterial, fungal and viral pathogens in cells of the human innate immune system. However, vitamin D also mediates potent tolerogenic effects: it is generally believed that vitamin D attenuates inflammation and acquired immunity, and thus potentially limits collateral tissue damage. Nevertheless, several studies indicate that vitamin D promotes aspects of acquired host defense. Clinically, vitamin D deficiency has been associated with an increased risk for various infectious diseases in epidemiological studies; yet, robust data from controlled trials investigating the use of vitamin D as a preventive or therapeutic agent are missing. In this review, we summarize the current knowledge regarding the effect of vitamin D on innate and acquired host defense, and speculate on the difficulties to translate the available molecular medicine data into practical therapeutic or preventive recommendations.

The human cytomegalovirus lytic cycle is induced by 1,25-dihydroxyvitamin D3 in peripheral blood monocytes and in the THP-1 monocytic cell line

Human cytomegalovirus (HCMV) resides in a latent form in hematopoietic progenitors and undifferentiated cells within the myeloid lineage. Maturation and differentiation along the myeloid lineage triggers lytic replication. Here, we used peripheral blood monocytes and the monocytic cell line THP-1 to investigate the effects of 1,25-dihydroxyvitamin D3 on HCMV replication. Interestingly, 1,25-dihydroxyvitamin D3 induces lytic replication marked by upregulation of HCMV gene expression and production of infectious virus. Moreover, we demonstrate that the effects of 1,25-dihydroxyvitamin D3 correlate with maturation/differentiation of the monocytes and not by directly stimulating the MIEP. These results are somewhat surprising as 1,25-dihydroxyvitamin D3 typically boosts immunity to bacteria and viruses rather than driving the infectious life cycle as it does for HCMV. Defining the signaling pathways kindled by 1,25-dihydroxyvitamin D3 will lead to a better understanding of the underlying molecular mechanisms that determine the fate of HCMV once it infects cells in the myeloid lineage.

Vitamin D and 1,25(OH)2D regulation of T cells

Vitamin D is a direct and indirect regulator of T cells. The mechanisms by which vitamin D directly regulates T cells are reviewed and new primary data on the effects of 1,25 dihydroxyvitamin D (1,25(OH)2D) on human invariant natural killer (iNK)T cells is presented. The in vivo effects of vitamin D on murine T cells include inhibition of T cell proliferation, inhibition of IFN-γ, IL-17 and induction of IL-4. Experiments in mice demonstrate that the effectiveness of 1,25(OH)2D requires NKT cells, IL-10, the IL-10R and IL-4. Comparisons of mouse and human T cells show that 1,25(OH)2D inhibits IL-17 and IFN-γ, and induces T regulatory cells and IL-4. IL-4 was induced by 1,25(OH)2D in mouse and human iNKT cells. Activation for 72 h was required for optimal expression of the vitamin D receptor (VDR) in human and mouse T and iNKT cells. In addition, T cells are potential autocrine sources of 1,25(OH)2D but again only 48-72 h after activation. Together the data support the late effects of vitamin D on diseases like inflammatory bowel disease and multiple sclerosis where reducing IL-17 and IFN-γ, while inducing IL-4 and IL-10, would be beneficial.