Comparative histologic features among liver biopsies with biliary-pattern injury and confirmed clinical diagnoses.

Biliary-pattern injury in the liver (eg, duct injury, ductular reaction, cholestasis) can occur in several conditions, including primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), large duct obstruction (LDO), and drug-induced liver injury (DILI). While the histologic changes in these conditions have been individually well described, distinguishing among them remains often challenging, particularly when biopsy samples are limited in size, robust clinical information is unavailable, and/or the pathologist does not feel confident in evaluating liver disease. This study evaluated histologic features that could aid the diagnosis of biliary-pattern injury on biopsy. We reviewed 121 liver biopsies from clinically confirmed cases of PBC, PSC, chronic LDO, or DILI for multiple clinical and histologic parameters. The rates of these histologic findings were then compared among different entities. Onion-skin fibrosis was seen in 14% of PSC in comparison to 0%, 5%, and 0% of PBC, DILI, and chronic LDO (P = 0.031). Florid duct lesions were identified in 21% of PBC compared to 2% of PSC and 0% of DILI and LDO (P = 0.0065). Similarly, 42% of PBC showed lobular granulomas, compared to 7% of PSC, 11% of DILI, and 33% of chronic LDO (P = 0.0001). Cholestasis was more commonly seen in DILI (42%) and chronic LDO (83%) than in PBC (4%) and PSC (16%) (P < 0.0001). Lobular chronic inflammation was found in a significantly higher percentage of PBC and LDO than of PSC and DILI (P = 0.0009). There were significantly fewer cases of PBC showing neutrophils in ductular reaction than PSC, DILI, and LDO (P = 0.0063). Histologic findings that can help suggest a diagnosis in liver biopsies with biliary-pattern injury include florid duct lesions, lobular granulomas, lack of neutrophils in ductular reaction, and lobular chronic inflammation in PBC; onion-skin fibrosis in PSC; cholestasis and feathery degeneration in DILI; and lobular granulomas, lobular chronic inflammation, cholestasis, and feathery degeneration in chronic LDO. These findings are likely most helpful when complicating factors interfere with biopsy interpretation.

The diagnostic utility of methylthioadenosine phosphorylase immunohistochemistry for pancreatic ductal adenocarcinoma in FNA and small biopsy specimens.

BACKGROUND: Accurate diagnosis of pancreatic lesions by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) or fine-needle biopsy can be challenging. Although surrogate immunohistochemical markers for genetic alterations associated with pancreatic ductal adenocarcinoma (PDAC) have been identified, they have modest sensitivity. Biallelic loss of CDKN2A occurs in up to 46% of PDACs, and methylthioadenosine phosphorylase (MTAP) immunohistochemistry (IHC) has been identified as a reliable surrogate marker for this alteration. The current study evaluates the utility of MTAP IHC for the diagnosis of PDAC. METHODS: In total, 136 cases of EUS-FNA cell block or core biopsy targeting solid pancreatic masses were identified. MTAP IHC was performed and evaluated for complete loss of expression in neoplastic cells. These results were correlated with available clinical next-generation sequencing that was performed on a subset of cases. RESULTS: Complete loss of MTAP expression was identified in 23 of 80 (29%) PDACs. A subset of cases classified as suspicious (4 of 21) and atypical (4 of 22) showed MTAP loss. All morphologically indeterminate cases with MTAP loss were confirmed as PDAC on resection/additional sampling. No benign samples (n = 13) showed loss of MTAP. In samples that had available clinical next-generation sequencing data (n = 13), copy number loss of CDKN2A was detected in all cases that had loss of MTAP expression (n = 4). CONCLUSIONS: Loss of MTAP was identified in approximately 30% of PDAC small biopsy specimens. As loss of MTAP expression is not expected in nonneoplastic cells, and these findings suggest that MTAP IHC can support a diagnosis of PDAC in small biopsy samples.

Large cell calcifying Sertoli cell tumour: molecular and immunohistochemical assessment of a series comprising non-metastasising and metastasising neoplasms.

Large cell calcifying Sertoli cell tumour (LCCSCT) is a type of testicular sex cord-stromal tumour that may occur sporadically or in the context of Carney complex and other genetic syndromes. A subset is clinically malignant, and the molecular mechanisms that drive such aggressive behaviour remain unknown. METHODS AND RESULTS: We analysed 21 samples from 20 patients with LCCSCT (12 non-metastasising and eight metastasising) using PRKAR1A immunohistochemistry (IHC) and next-generation sequencing. All tumours except two (cases 17 and 20, both metastasising) demonstrated loss of PRKAR1A expression. Among 11 cases with interpretable sequencing results, all harboured pathogenic single nucleotide variants of PRKAR1A. Evidence of loss of heterozygosity (LOH) of PRKAR1A was present in all tumours with interpretable zygosity data, but the mechanisms of LOH were different for non-metastasising and metastasising tumours. Non-metastasising tumours demonstrated only copy-neutral LOH, while metastasising tumours demonstrated a spectrum of mechanisms of LOH, including copy-loss LOH, two concurrent mutations or copy-neutral LOH. Relevant molecular findings in non-metastasising LCCSCT were limited to PRKAR1A variants. In contrast, all metastasising LCCSCTs with interpretable data harboured additional pathogenic variants, including (but not restricted to) BRCA2 mutations with evidence of LOH and bi-allelic CDKN2A/B deletions. Three patients harboured PRKAR1A variants of inferred germline origin, including one with Carney complex and two without known syndromic features. CONCLUSIONS: This study further confirms that PRKAR1A IHC is a useful diagnostic tool for both non-metastasising and metastasising tumours and suggests that molecular analyses can be helpful to identify non-metastasising tumours with malignant potential in selected patients. Importantly, these results highlight that germline assessment could be beneficial for all patients presenting with LCCSCT.

"Malignant Mesenchymoma" Revisited: A Clinicopathologic Study of Leiomyosarcomas With Osteosarcomatous Differentiation.

Leiomyosarcoma (LMS) is the most common sarcoma in adults. Rarely, LMS dedifferentiates into an undifferentiated sarcoma. Very few cases of LMS with heterologous osteosarcomatous differentiation (OS) have been reported. The purpose of this study was to evaluate the clinicopathologic features of LMS with OS. Of 5570 LMS cases diagnosed from 2006 to 2022, 15 cases (0.2%) of LMS with OS were identified, affecting 13 females and 2 males; ages ranged from 32 to 66 years (median: 53 y). Ten tumors arose in the uterus, 2 in the retroperitoneum, and 1 each in the mesentery, mediastinum, and rectum. Primary tumors ranged from 7 to 20 cm (mean: 16 cm). The LMS components showed conventional spindle cell morphology in most cases; 3 cases showed marked pleomorphism; 3 cases contained an epithelioid component; and 1 case showed myxoid features. In 5 cases OS was identified in the primary tumor, whereas in 10 cases OS was first detected in metastases. One metastatic and 2 primary LMS showed both OS and chondrosarcomatous differentiation. Prominent osteoclastic giant cells were seen in the OS components in 11 cases. Mitotic activity ranged from 17 to 61/10 HPF with tumor necrosis in 10 cases. Twelve patients developed metastases; sites included lungs, diaphragm, kidney, adrenal glands, colon, small intestine, liver, bone, and pancreas. At last follow-up, 8 patients had died of disease, and 4 patients were alive with metastases. The interval between OS and death ranged from 3 weeks to 18 months (median: 6.5 mo). Development of OS in LMS is exceptionally rare. This form of heterologous differentiation may occur in both primary tumors and metastases. LMS with OS is highly aggressive with poor outcomes. Awareness of this phenomenon is important to avoid misdiagnosis as osteosarcoma.

Chloroma of the Bladder: A Case Report of Leukemia Progression Presenting as Hematuria.

Myeloid sarcoma (MS) is a rare extramedullary manifestation of acute myelogenous leukemia (AML). The mass is composed of primitive myeloid cells that can occur in a variety of organs, most commonly the skin, lymph nodes, GI tract, bone, breast, and CNS. Involvement of the genitourinary tract is rare. Consensus on treatment of MS has not been established, but management typically involves systemic therapy, such as chemotherapy or allogeneic hematopoietic stem cell transplant as well as palliative local therapies such as radiation or surgery. Outcomes of MS using novel AML therapies, such as BCL-2 inhibitors or IDH inhibitors, remain undescribed. We describe a rare case of a 70-year-old man presenting with MS of the urinary bladder complicating known secondary AML (RUNX1 and IDH2 mutated). Prior to development of bladder MS, the patient had received decitabine, enasidenib, and venetoclax. Following diagnosis, he was treated with cytarabine and venetoclax. To our knowledge, this is the first case of bladder MS treated with a BCL-2 inhibitor.

An algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A can help differentiate between gastrointestinal and pulmonary neuroendocrine carcinomas.

Primary gastrointestinal neuroendocrine carcinoma (GI-NEC) cannot be distinguished morphologically from pulmonary neuroendocrine carcinoma (P-NEC). This can present a significant diagnostic challenge in cases where site of origin cannot be readily determined. To identify immunohistochemical (IHC) markers that can be used to reliably distinguish between GI-NECs and P-NECs, we constructed 3-mm tissue microarrays, one containing 13 GI-NECs and one containing 20 P-NECs. IHC was performed on both microarrays using 21 stains: AE1/AE3, CK7, CK20, synaptophysin, chromogranin, CD56, INSM1, SSTR2A, CDX2, SATB2, TTF1, Napsin A, PR, GATA3, PAX8, ISL1, beta-catenin, AFP, SMAD4, Rb, and p53. For GI-NEC, the most strongly expressed marker was synaptophysin (mean H-score 248), while AE1/AE3 was the most strongly expressed in P-NEC (mean H-score 230), which was stronger than in GI-NEC (p = 0.011). Other markers that were stronger overall in P-NEC than in GI-NEC included CK7 (p < 0.0001) and TTF1 (p < 0.0001). Markers that were stronger overall in GI-NEC than in P-NEC included SSTR2A (p = 0.0021), SATB2 (p = 0.018), CDX2 (p = 0.019), and beta-catenin (nuclear; p = 0.029). SMAD4, Rb, and p53 showed similar rates of abnormal protein expression. Based on these results, a stepwise algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A had a 91% overall accuracy in distinguishing these GI-NEC from P-NEC. This was tested on a second cohort of 10 metastatic GI-NEC and 10 metastatic P-NEC, with an accuracy in this cohort of 85% and an overall accuracy of 89% for the 53 cases tested. Our algorithm reasonably discriminates GI-NEC from P-NEC using currently available IHC stains.

Blockade of RGMb inhibits allergen-induced airways disease.

BACKGROUND: Allergic asthma causes morbidity in many subjects, and novel precision-directed treatments would be valuable. OBJECTIVE: We sought to examine the role of a novel innate molecule, repulsive guidance molecule b (RGMb), in murine models of allergic asthma. METHODS: In models of allergic asthma using ovalbumin or cockroach allergen, mice were treated with anti-RGMb or control mAb and examined for airway inflammation and airway hyperreactivity (AHR), a cardinal feature of asthma. The mechanisms by which RGMb causes airways disease were also examined. RESULTS: We found that blockade of RGMb by treatment with anti-RGMb mAb effectively blocked the development of airway inflammation and AHR. Importantly, blockade of RGMb completely blocked the development of airway inflammation and AHR, even if treatment occurred only during the challenge (effector) phase. IL-25 played an important role in these models of asthma because IL-25 receptor-deficient mice did not develop disease after sensitization and challenge with allergen. RGMb was expressed primarily by innate cells in the lungs, including bronchial epithelial cells (known producers of IL-25), activated eosinophils, and interstitial macrophages, which in the inflamed lung expressed the IL-25 receptor and produced IL-5 and IL-13. We also found that neogenin, the canonical receptor for RGMb, was expressed by interstitial macrophages and bronchial epithelial cells in the inflamed lung, suggesting that an innate RGMb-neogenin axis might modulate allergic asthma. CONCLUSIONS: These results demonstrate an important role for a novel innate pathway in regulating type 2 inflammation in patients with allergic asthma involving RGMb and RGMb-expressing cells, such as interstitial macrophages and bronchial epithelial cells. Moreover, targeting this previously unappreciated innate pathway might provide an important treatment option for allergic asthma.

Innate immunity in the lung regulates the development of asthma.

The lung, while functioning as a gas exchange organ, encounters a large array of environmental factors, including particulate matter, toxins, reactive oxygen species, chemicals, allergens, and infectious microbes. To rapidly respond to and counteract these elements, a number of innate immune mechanisms have evolved that can lead to lung inflammation and asthma, which is the focus of this review. These innate mechanisms include a role for two incompletely understood cell types, invariant natural killer T (iNKT) cells and innate lymphoid cells (ILCs), which together produce a wide range of cytokines, including interleukin-4 (IL-4), IL-5, IL-13, interferon-γ, IL-17, and IL-22, independently of adaptive immunity and conventional antigens. The specific roles of iNKT cells and ILCs in immunity are still being defined, but both cell types appear to play important roles in the lungs, particularly in asthma. As we gain a better understanding of these innate cell types, we will acquire great insight into the mechanisms by which allergic and non-allergic asthma phenotypes develop.

RGMb is a novel binding partner for PD-L2 and its engagement with PD-L2 promotes respiratory tolerance.

We report that programmed death ligand 2 (PD-L2), a known ligand of PD-1, also binds to repulsive guidance molecule b (RGMb), which was originally identified in the nervous system as a co-receptor for bone morphogenetic proteins (BMPs). PD-L2 and BMP-2/4 bind to distinct sites on RGMb. Normal resting lung interstitial macrophages and alveolar epithelial cells express high levels of RGMb mRNA, whereas lung dendritic cells express PD-L2. Blockade of the RGMb-PD-L2 interaction markedly impaired the development of respiratory tolerance by interfering with the initial T cell expansion required for respiratory tolerance. Experiments with PD-L2-deficient mice showed that PD-L2 expression on non-T cells was critical for respiratory tolerance, but expression on T cells was not required. Because PD-L2 binds to both PD-1, which inhibits antitumor immunity, and to RGMb, which regulates respiratory immunity, targeting the PD-L2 pathway has therapeutic potential for asthma, cancer, and other immune-mediated disorders. Understanding this pathway may provide insights into how to optimally modulate the PD-1 pathway in cancer immunotherapy while minimizing adverse events.

Innate lymphoid cells and asthma.

Asthma is a complex and heterogeneous disease with several phenotypes, including an allergic asthma phenotype characterized by TH2 cytokine production and associated with allergen sensitization and adaptive immunity. Asthma also includes nonallergic asthma phenotypes, such as asthma associated with exposure to air pollution, infection, or obesity, that require innate rather than adaptive immunity. These innate pathways that lead to asthma involve macrophages, neutrophils, natural killer T cells, and innate lymphoid cells, newly described cell types that produce a variety of cytokines, including IL-5 and IL-13. We review the recent data regarding innate lymphoid cells and their role in asthma.

Invariant NKT cell defects in vitamin D receptor knockout mice prevents experimental lung inflammation.

Vitamin D receptor (VDR) deficiency (knockout [KO]) results in a failure of mice to generate an airway hyperreactivity (AHR) response on both the BALB/c and C57BL/6 background. The cause of the failed AHR response is the defective population of invariant NKT (iNKT) cells in the VDR KO mice because wild-type (WT) iNKT cells rescued the AHR response. VDR KO mice had significantly fewer iNKT cells and normal numbers of T cells in the spleen compared with WT mice. In BALB/c VDR KO mice, the reduced frequencies of iNKT cells were not apparent in the liver or thymus. VDR KO and WT Th2 cells produced similar levels of IFN-γ and IL-5. On the BALB/c background, Th2 cells from VDR KO mice produced less IL-13, whereas on the C57BL/6 background, Th2 cells from VDR KO mice produced less IL-4. Conversely, VDR KO iNKT cells were defective for the production of multiple cytokines (BALB/c: IL-4, IL-5, and IL-13; C57BL/6: IL-4 and IL-17). Despite relatively normal Th2 responses, BALB/c and C57BL/6 VDR KO mice failed to develop AHR responses. The defect in iNKT cells as a result of the VDR KO was more important than the highly susceptible Th2 background of the BALB/c mice. Defective iNKT cell responses in the absence of the VDR result in the failure to generate AHR responses in the lung. The implication of these mechanistic findings for human asthma requires further investigation.

Converging pathways lead to overproduction of IL-17 in the absence of vitamin D signaling.

Multiple pathways converge to result in the overexpression of T(h)17 cells in the absence of either vitamin D or the vitamin D receptor (VDR). CD4(+) T cells from VDR knockout (KO) mice have a more activated phenotype than their wild-type (WT) counterparts and readily develop into T(h)17 cells under a variety of in vitro conditions. Vitamin D-deficient CD4(+) T cells also overproduced IL-17 in vitro and 1,25 dihydroxyvitamin D(3) inhibited the development of T(h)17 cells in CD4(+) T-cell cultures. Conversely, the induction of inducible (i) Tregs was lower in VDR KO CD4(+) T cells than WT and the VDR KO iTregs were refractory to IL-6 inhibition. Host-specific effects of the VDR were evident on in vivo development of naive T cells. Development of naive WT CD4(+) T cells in the VDR KO host resulted in the overexpression of IL-17 and more severe experimental inflammatory bowel disease (IBD). The increased expression of T(h)17 cells in the VDR KO mice was associated with a reduction in tolerogenic CD103(+) dendritic cells. The data collectively demonstrate that T(h)17 and iTreg cells are direct and indirect targets of vitamin D. The increased propensity for development of T(h)17 cells in the VDR KO host results in more severe IBD.

Epigenetic reduction in invariant NKT cells following in utero vitamin D deficiency in mice.

Vitamin D status changes with season, but the effect of these changes on immune function is not clear. In this study, we show that in utero vitamin D deficiency in mice results in a significant reduction in invariant NKT (iNKT) cell numbers that could not be corrected by later intervention with vitamin D or 1,25-dihydroxy vitamin D(3) (active form of the vitamin). Furthermore, this was intrinsic to hematopoietic cells, as vitamin D-deficient bone marrow is specifically defective in generating iNKT cells in wild-type recipients. This vitamin D deficiency-induced reduction in iNKT cells is due to increased apoptosis of early iNKT cell precursors in the thymus. Whereas both the vitamin D receptor and vitamin D regulate iNKT cells, the vitamin D receptor is required for both iNKT cell function and number, and vitamin D (the ligand) only controls the number of iNKT cells. Given the importance of proper iNKT cell function in health and disease, this prenatal requirement for vitamin D suggests that in humans, the amount of vitamin D available in the environment during prenatal development may dictate the number of iNKT cells and potential risk of autoimmunity.

Interleukin-2-inducible T cell kinase (Itk) network edge dependence for the maturation of iNKT cell.

Invariant natural killer T (iNKT) cells are a unique subset of innate T lymphocytes that are selected by CD1d. They have diverse immune regulatory functions via the rapid production of interferon-γ (IFN-γ) and interleukin-4 (IL-4). In the absence of signaling nodes Itk and Txk, Tec family non-receptor tyrosine kinases, mice exhibit a significant block in iNKT cell development. We now show here that although the Itk node is required for iNKT cell maturation, the kinase domain edge of Itk is not required for continued maturation iNKT cells in the thymus compared with Itk-null mice. This rescue is dependent on the expression of the Txk node. Furthermore, this kinase domain independent edge rescue correlates with the increased expression of the transcription factors T-bet, the IL-2/IL-15 receptor ß chain CD122, and suppression of eomesodermin expression. By contrast, α-galactosyl ceramide induced cytokine secretion is dependent on the kinase domain edge of Itk. These findings indicate that the Itk node uses a kinase domain independent edge, a scaffolding function, in the signaling pathway leading to the maturation of iNKT cells. Furthermore, the findings indicate that phosphorylation of substrates by the Itk node is only partially required for maturation of iNKT cells, while functional activation of iNKT cells is dependent on the kinase domain/activity edge of Itk.

Vitamin D and host resistance to infection? Putting the cart in front of the horse.

Vitamin D is being touted as an anti-infective agent and it has even been suggested that vitamin D supplementation could be effective against the H1N1 influenza virus. The claims are largely based on the ability of vitamin D to induce antibacterial peptides and evidence that the immune system produces active vitamin D (1,25(OH)(2)D(3)) in situ. While there are many examples of immune production of 1,25(OH)(2)D(3) in vitro, there is little in vivo evidence. In addition, it is not clear what role immune production of 1,25(OH)(2)D(3) has on the course of disease. Vitamin D and 1,25(OH)(2)D(3) inhibit T helper type 1 (Th1)/Th17-mediated immune responses and autoimmune diseases by acting on the innate and acquired immune system to inhibit the function of Th1 and Th17 cells. Th1 and Th17 cells are important in host resistance to many infections including tuberculosis (TB) caused by Mycobacterium tuberculosis. Paradoxically the innate immune system is induced to produce antibacterial peptides that are effective against TB in vitro. Data from several models of infection have so far not supported a role for vitamin D in affecting the course of disease. There is also very little evidence that vitamin D affects the course of human TB infection. Experiments have not been done in cells, mice or humans to evaluate the effect of vitamin D on influenza virus. At this time it would be premature to claim that vitamin D has an effect on TB, influenza or any other infection.

The effects of whole mushrooms during inflammation.

BACKGROUND: Consumption of edible mushrooms has been suggested to improve health. A number of isolated mushroom constituents have been shown to modulate immunity. Five commonly consumed edible mushrooms were tested to determine whether whole mushrooms stimulate the immune system in vitro and in vivo. RESULTS: The white button (WB) extracts readily stimulated macrophage production of TNF-alpha. The crimini, maitake, oyster and shiitake extracts also stimulated TNF-alpha production in macrophage but the levels were lower than from WB stimulation. Primary cultures of murine macrophage and ovalbumin (OVA) specific T cells showed that whole mushroom extracts alone had no effect on cytokine production but co-stimulation with either lipopolysaccharide or OVA (respectively) induced TNF-alpha, IFN-gamma, and IL-1beta while decreasing IL-10. Feeding mice diets that contained 2% WB mushrooms for 4 weeks had no effect on the ex vivo immune responsiveness or associated toxicity (changes in weight or pathology of liver, kidney and gastrointestinal tract). Dextran sodium sulfate (DSS) stimulation of mice that were fed 1% WB mushrooms were protected from DSS induced weight loss. In addition, 2% WB feeding protected the mice from transient DSS induced colonic injury. The TNF-alpha response in the colon and serum of the DSS challenged and 2% WB fed mice was higher than controls. CONCLUSION: The data support a model whereby edible mushrooms regulate immunity in vitro. The in vivo effects of edible mushrooms required a challenge with DSS to detect small changes in TNF-alpha and transient protection from colonic injury. There are modest effects of in vivo consumption of edible mushrooms on induced inflammatory responses. The result is not surprising since it would certainly be harmful to strongly induce or suppress immune function following ingestion of a commonly consumed food.

Failure of T cell homing, reduced CD4/CD8alphaalpha intraepithelial lymphocytes, and inflammation in the gut of vitamin D receptor KO mice.

Specific pathogen-free IL-10 KO mice failed to develop inflammatory bowel disease (IBD), whereas IL-10/vitamin D receptor (VDR) double KO mice developed fulminating IBD. WT CD4 T cells inhibited experimental IBD, while VDR KO CD4 T cells failed to suppress IBD. VDR KO mice had normal numbers and functions of regulatory T cells. The percentages of IL-17- and IFN-gamma-secreting T cells in the gut of mice reconstituted with WT and VDR KO CD4 T cells were also not different. Instead, there were twice as many CD8alphaalpha intraepithelial lymphocytes (IEL) in mice that were reconstituted with WT CD4 T cells than in mice reconstituted with VDR KO CD4 T cells. Furthermore, VDR KO mice had reduced numbers of CD8alphaalpha IEL, absent CD4/CD8alphaalpha populations, and as a result low IL-10 production in the IEL. The lack of CD8alphaalpha IEL was due in part to decreased CCR9 expression on T cells that resulted in the failure of the VDR KO T cells to home to the small intestine. We conclude that the VDR mediates T cell homing to the gut and as a result the VDR KO mouse has reduced numbers of CD8alphaalpha IEL with low levels of IL-10 leading to increased inflammatory response to the normally harmless commensal flora.

The paradoxical effects of vitamin D on type 1 mediated immunity.

Low vitamin D status is associated with an increased risk of Th1 mediated autoimmune diseases like inflammatory bowel disease. 1,25(OH)(2)D(3) treatments have been shown to suppress Th1 mediated immunity and protect animals from experimental autoimmunity. Th1 mediated immunity is important for clearance of a number of different infectious diseases. For tuberculosis 1,25(OH)(2)D(3) treatment is associated with decreased Th1 mediated immunity but increased bactericidal activity. Systemic candidiasis is unaffected by 1,25(OH)(2)D(3) treatment. The seemingly paradoxical effects of 1,25(OH)(2)D(3) and vitamin D on Th1 mediated autoimmunity versus infectious immunity point to a broad array of vitamin D targets in the immune system. The interplay of these vitamin D targets and their impact on the host-immune response then dictate the outcome.

The vitamin D receptor is required for iNKT cell development.

CD1d-reactive natural killer T (NKT) cells with an invariant T cell receptor Valpha14 rearrangement are a unique subset of lymphocytes, which play important roles in immune regulation, tumor surveillance, and host defense against pathogens. Vitamin D is a nutrient/hormone that has been shown to regulate conventional T cell responses but not T cell development. The data show that expression of the vitamin D receptor (VDR) is required for normal development and function of iNKT cells. The iNKT cells from VDR KO mice are intrinsically defective and lack T-bet expression. VDR KO iNKT cells fail to express NK1.1, although they express normal levels of CD122. Extrinsic factors that impact iNKT cell development and function in VDR KO mice include a failure of the liver to support homeostatic proliferation and reduced thymic expression of CD1d and other factors important for optimal antigen presentation in the thymus. In addition, VDR KO iNKT cells were intrinsically defective even when WT antigen-presenting cells were used to stimulate them.

All-trans retinoic acid biases immune response induced by DNA vaccine in a Th2 direction.

Vitamin A deficiency diminishes Th2-mediated Ab responses. Providing Vitamin A or its active metabolites reverses this defect. All-trans retinoic acid (ATRA), an acid derivation of Vitamin A, regulates the balance of immune response induced by TR421-hCGbeta DNA vaccine. Compared to DNA vaccine alone or treatment with vehicle, significantly higher level of antibody against the protein encoded by DNA vaccine was observed in mice 6 weeks after the first immunization. The IgG2a/IgG1 ratio was lower in mice treated with ATRA. We also found that treatment with ATRA also diminishes specific cellular immune response induced by gene immunization by measuring the marker of cellular immune response. We conclude that ATRA biases the immune response to Th2 direction induced by DNA vaccine and acts as a candidate adjuvant and immunomodulatory molecule.