CD1d expression on and regulation of murine hematopoietic stem and progenitor cells

Experimental Models of Mouse and Human Hematopoietic Stem Cell Transplantation

Experimental hematopoietic stem cell transplantation (HSCT) is an invaluable tool in determining the function and characteristics of hematopoietic stem cells (HSC) from experimental mouse and human donor groups. These groups could include, but are not limited to, genetically altered populations (gene knockout/knockin models), ex vivo manipulated cell populations, or in vivo modulated cell populations. The basic fundamentals of this process involve taking cells from a mouse/human donor source and putting them into another mouse (recipient) after preconditioning of the recipient with either total body irradiation (TBI) for mouse donor cells or into sublethally irradiated immune-deficient mice for human donor cells. Then, at pre-determined time points post-transplant, sampling a small amount of peripheral blood (PB) and at the termination of the evalaution, bone marrow (BM) to determine donor contribution and function by phenotypic analysis. Exploiting the congenic mouse strains of C57BL/6 (CD45.1^- CD45.2⁺), BoyJ (CD45.1⁺ CD45.2^-), and their F1-crossed hybrid C57BL/6 × BoyJ (CD45.1⁺ CD45.2⁺), we are able to quantify donor, competitor, and recipient mouse cell contributions to the engraftment state. Human donor cell engraftment (e.g., from the cord blood [CB], mobilized PB, or BM) is assessed by human cell phenotyping in sublethally irradiated immune-deficient mouse recipients (e.g., NOD scid gamma mice that are deficient in B cells, T cells, and natural killer cells and have defective dendritic cells and macrophages). Engraftment of cells from primary mouse recipients into secondary mice allows for an estimation of the self-renewal capacity of the original donor HSC. This chapter outlines concepts, methods, and techniques for mouse and human cell models of HSCT and for assessment of donor cells collected and processed in hypoxia versus ambient air.

Chromatin remodeling subunit BRM and valine regulate hematopoietic stem/progenitor cell function and self-renewal via intrinsic and extrinsic effects

Little is known of hematopoietic stem (HSC) and progenitor (HPC) cell self-renewal. The role of Brahma (BRM), a chromatin remodeler, in HSC function is unknown. Bone marrow (BM) from Brm^-/- mice manifested increased numbers of long- and short-term HSCs, GMPs, and increased numbers and cycling of functional HPCs. However, increased Brm^-/- BM HSC numbers had decreased secondary and tertiary engraftment, suggesting BRM enhances HSC self-renewal. Valine was elevated in lineage negative Brm^-/- BM cells, linking intracellular valine with Brm expression. Valine enhanced HPC colony formation, replating of human cord blood (CB) HPC-derived colonies, mouse BM and human CB HPC survival in vitro, and ex vivo expansion of normal mouse BM HSCs and HPCs. Valine increased oxygen consumption rates of WT cells. BRM through CD98 was linked to regulated import of branched chain amino acids, such as valine, in HPCs. Brm^-/- LSK cells exhibited upregulated interferon response/cell cycle gene programs. Effects of BRM depletion are less apparent on isolated HSCs compared to HSCs in the presence of HPCs, suggesting cell extrinsic effects on HSCs. Thus, intracellular valine is regulated by BRM expression in HPCs, and the BRM/valine axis regulates HSC and HPC self-renewal, proliferation, and possibly differentiation fate decisions.

Expression of NR5A2, NUP153, HNF4A, USP15 and FNDC3B is consistent with their use as novel biomarkers for bovine mammary stem/progenitor cells

Mammary stem cells (MaSC) are essential for growth and maintenance of mammary epithelium. Previous studies have utilized morphological characteristics or retention of bromodeoxyuridine (BrdU) label to identify MaSC and progenitor cells, these approaches may not be feasible or may not identify all resident stem cells. Alternatively, these special cells may be identified by assessing protein and mRNA expression of appropriate markers. The focus of this study was to assess the staining patterns and in situ quantification of novel candidate markers for bovine MaSC/progenitor cells. The candidate markers for MaSC/progenitor cells for immunohistochemical analysis were: NR5A2, NUP153, HNF4A, USP15 and FNDC3B and for in situ transcripts quantification were HNF4A and NUP153. We also evaluated protein expression pattern of presumptive MaSC markers known from the literature namely, ALDH1, MSI1 and Notch3. We found that NR5A2, NUP153, HNF4A and USP15-labeled cells represented 2.5-6% of epithelial cells prepubertally and were distributed in a fashion consistent with the location and abundance of MaSC/progenitor cells. A transient increase (10-37%) in expression of these markers was observed at peak lactation. FNDC3B was localized mainly in the nucleus prepubertally and in the cytoplasm of myoepithelial cells and nuclei of a limited number of alveolar cells during lactation. Abundant expression (~ 48%) and luminal localization of ALDH1 precludes its use as a bovine MaSC marker but may include transamplifying progenitor cells. MSI1 staining was consistent with MaSC localization. Onset of lumen formation in mammary ducts of prepubertal gland was associated with Notch 3 expression in the apical surface of luminal cells. RNAscope analysis of HNF4A and NUP153 transcripts in calf mammary gland showed very low copy numbers in a few epithelial cells, supporting the idea that these markers are expressed by fewer cells of epithelial origin. This study suggests that NR5A2, NUP153, HNF4A, USP15 and FNDC3B are likely markers for bovine MaSC/progenitor cells. Quantification of RNA transcripts of HNF4A and NUP153 in bovine MEC as potential MaSC markers are novel. Further studies to correlate protein expression of these markers with their transcripts level using single cell analysis in larger samples in lactating cow at different physiological stages are warranted.

Biology of CD1- and MR1-restricted T cells

Over the past 15 years, investigators have shown that T lymphocytes can recognize not only peptides in the context of MHC class I and class II molecules but also foreign and self-lipids in association with the nonclassical MHC class I-like molecules, CD1 proteins. In this review, we describe the most recent events in the field, with particular emphasis on (a) structural and functional aspects of lipid presentation by CD1 molecules, (b) the development of CD1d-restricted invariant natural killer T (iNKT) cells and transcription factors required for their differentiation, (c) the ability of iNKT cells to modulate innate and adaptive immune responses through their cross talk with lymphoid and myeloid cells, and (d) MR1-restricted and group I (CD1a, CD1b, and CD1c)-restricted T cells.

Adjuvanted poly(lactic-co-glycolic) acid nanoparticle-entrapped inactivated porcine reproductive and respiratory syndrome virus vaccine elicits cross-protective immune response in pigs

Porcine reproductive and respiratory syndrome (PRRS), caused by the PRRS virus (PRRSV), is an economically devastating disease, causing daily losses of approximately $3 million to the US pork industry. Current vaccines have failed to completely prevent PRRS outbreaks. Recently, we have shown that poly(lactic-co-glycolic) acid (PLGA) nanoparticle-entrapped inactivated PRRSV vaccine (NP-KAg) induces a cross-protective immune response in pigs. To further improve its cross-protective efficacy, the NP-KAg vaccine formulation was slightly modified, and pigs were coadministered the vaccine twice intranasally with a potent adjuvant: Mycobacterium tuberculosis whole-cell lysate. In vaccinated virulent heterologous PRRSV-challenged pigs, the immune correlates in the blood were as follows: 1) enhanced PRRSV-specific antibody response with enhanced avidity of both immunoglobulin (Ig)-G and IgA isotypes, associated with augmented virus-neutralizing antibody titers; 2) comparable and increased levels of virus-specific IgG₁ and IgG₂ antibody subtypes and production of high levels of both T-helper (Th)-1 and Th2 cytokines, indicative of a balanced Th1–Th2 response; 3) suppressed immunosuppressive cytokine response; 4) increased frequency of interferon-γ⁺ lymphocyte subsets and expanded population of antigen-presenting cells; and most importantly 5) complete clearance of detectable replicating challenged heterologous PRRSV and close to threefold reduction in viral ribonucleic acid load detected in the blood. In conclusion, intranasal delivery of adjuvanted NP-KAg vaccine formulation to growing pigs elicited a broadly cross-protective immune response, showing the potential of this innovative vaccination strategy to prevent PRRS outbreaks in pigs. A similar approach to control other respiratory diseases in food animals and humans appears to be feasible.

Preclinical evaluation of invariant natural killer T cells in the 5T33 multiple myeloma model

Immunomodulators have been used in recent years to reactivate host anti-tumor immunity in several hematological malignancies. This report describes the effect of activating natural killer T (NKT) cells by α-Galactosylceramide (α-GalCer) in the 5T33MM model of multiple myeloma (MM). NKT cells are T lymphocytes, co-expressing T and NK receptors, while invariant NKT cells (iNKTs) also express a unique semi-invariant TCR α-chain. We followed iNKT numbers during the development of the disease in both 5T33MM mice and MM patients and found that their numbers dropped dramatically at the end stage of the disease, leading to a loss of total IFN-γ secretion. We furthermore observed that α-GalCer treatment significantly increased the survival of 5T33MM diseased mice. Taken together, our data demonstrate for the first time the possibility of using a preclinical murine MM model to study the effects of α-GalCer and show promising results of α-GalCer treatment in a low tumor burden setting.

Glycosylphosphatidylinositol-specific, CD1d-restricted T cells in paroxysmal nocturnal hemoglobinuria

The mechanism of bone marrow failure (BMF) in paroxysmal nocturnal hemoglobinuria (PNH) is not yet known. Because in PNH the biosynthesis of the glycolipid molecule glycosylphosphatidylinositol (GPI) is disrupted in hematopoietic stem and progenitor cells by a somatic mutation in the PIG-A gene, BMF might result from an autoimmune attack, whereby T cells target GPI in normal cells, whereas PIG-A mutant GPI-negative cells are spared. In a deliberate test of this hypothesis, we have demonstrated in PNH patients the presence of CD8(+) T cells reactive against antigen-presenting cells (APCs) loaded with GPI. These T cells were significantly more abundant in PNH patients than in healthy controls; their reactivity depended on CD1d expression and they increased upon coculture with CD1d-expressing, GPI-positive APCs. In GPI-specific T cells captured by CD1d dimer technology, we identified, through global T-cell receptor α (TCRα) analysis, an invariant TCRVα21 sequence, which was then found at frequencies higher than background in the TCR repertoire of 6 of 11 PNH patients. Thus, a novel, autoreactive, CD1d-restricted, GPI-specific T-cell population, enriched in an invariant TCRα chain, is expanded in PNH patients and may be responsible for BMF in PNH.

Activated invariant NKT cells control central nervous system autoimmunity in a mechanism that involves myeloid-derived suppressor cells

Invariant NKT (iNKT) cells are a subset of T lymphocytes that recognize glycolipid Ags presented by the MHC class I-related protein CD1d. Activation of iNKT cells with glycolipid Ags, such as the marine sponge-derived reagent α-galactosylceramide (α-GalCer), results in the rapid production of a variety of cytokines and activation of many other immune cell types. These immunomodulatory properties of iNKT cells have been exploited for the development of immunotherapies against a variety of autoimmune and inflammatory diseases, but mechanisms by which activated iNKT cells confer disease protection have remained incompletely understood. In this study, we demonstrate that glycolipid-activated iNKT cells cooperate with myeloid-derived suppressor cells (MDSCs) in protecting mice against the development of experimental autoimmune encephalomyelitis (EAE) in mice, an animal model for multiple sclerosis. We show that α-GalCer induced the expansion and immunosuppressive activities of MDSCs in the spleen of mice induced for development of EAE. Disease protection in these animals also correlated with recruitment of MDSCs to the CNS. Depletion of MDSCs abrogated the protective effects of α-GalCer against EAE and, conversely, adoptive transfer of MDSCs from α-GalCer-treated mice ameliorated passive EAE induced in recipient animals. The cytokines GM-CSF, IL-4, and IFN-γ, produced by activated iNKT cells, and inducible NO synthase, arginase-1, and IL-10 produced by MDSCs, contributed to these effects. Our findings have revealed cooperative immunosuppressive interactions between iNKT cells and MDSCs that might be exploited for the development of improved immunotherapies for multiple sclerosis and other autoimmune and inflammatory diseases.