Seokmann Hong

CD1d1 Mutant Mice Are Deficient in Natural T Cells That PromptlyProduce IL-4

Murine CD1 has been implicated in the development and function of an unusual subset of T cells, termed natural T (NT) cells, that coexpress the T cell receptor (TCR) and the natural killer cell receptor NK1.1. Activated NT cells promptly produce large amounts of IL-4, suggesting that these cells can influence the differentiation of CD4+ effector T cell subsets. We have generated mice that carry a mutant CD1d1 gene. NT cell numbers in the thymus, spleen, and liver of these mice were dramatically reduced. Activated splenocytes from mutant mice did not produce IL-4, whereas similarly treated wild-type splenocytes secreted large amounts of this cytokine. These results demonstrate a critical role for CD1 in the positive selection and function of NT cells.

The natural killer T-cell ligand α-galactosylceramide prevents autoimmune diabetes in non-obese diabetic mice

Diabetes in non-obese diabetic (NOD) mice is mediated by pathogenic T-helper type 1 (Th1) cells that arise because of a deficiency in regulatory or suppressor T cells. Vα14–Jα15 natural killer T (NKT) cells recognize lipid antigens presented by the major histocompatibility complex class I-like protein CD1d (refs. 3,4). We have previously shown that in vivo activation of Vα14 NKT cells by α-galactosylceramide (α-GalCer) and CD1d potentiates Th2-mediated adaptive immune responses. Here we show that α-GalCer prevents development of diabetes in wild-type but not CD1d-deficient NOD mice. Disease prevention correlated with the ability of α-GalCer to suppress interferon-γ but not interleukin-4 production by NKT cells, to increase serum immunoglobulin E levels, and to promote the generation of islet autoantigen-specific Th2 cells. Because α-GalCer recognition by NKT cells is conserved among mice and humans, these findings indicate that α-GalCer might be useful for therapeutic intervention in human diseases characterized by Th1-mediated pathology such as Type 1 diabetes.

Natural killer cells determine the outcome of B cell-mediated autoimmunity.

Natural killer (NK) cells can affect the outcome of adaptive immune responses. NK cells, but not NK1.1+ T cells, were found to participate in the development of myasthenia gravis (a T cell–dependent, B cell– and antibody-mediated autoimmune disease) in C57BL/6 mice. The requirement for NK cells was reflected by the lack of a type 1 helper T cell response and antibodies to the acetylcholine receptor in both NK1.1+ cell–depleted and NK cell–deficient IL-18−/− mice. These findings establish a previously unrecognized link between NK cells and autoreactive T and B cells.

NK T Cells Contribute to Expansion of CD8+ T Cells and Amplification of Antiviral Immune Responses to Respiratory Syncytial Virus

ABSTRACT CD1d-deficient mice have normal numbers of T lymphocytes and natural killer cells but lack Vα14+ natural killer T cells. Respiratory syncytial virus (RSV) immunopathogenesis was evaluated in 129×C57BL/6, C57BL/6, and BALB/c CD1d−/− mice. CD8+ T lymphocytes were reduced in CD1d−/− mice of all strains, as shown by cell surface staining and major histocompatibility complex class I tetramer analysis, and resulted in strain-specific alterations in illness, viral clearance, and gamma interferon (IFN-γ) production. Transient activation of NK T cells in CD1d+/+ mice by α-GalCer resulted in reduced illness and delayed viral clearance. These data suggest that early IFN-γ production and efficient induction of CD8+-T-cell responses during primary RSV infection require CD1d-dependent events. We also tested the ability of α-GalCer as an adjuvant to modulate the type 2 immune responses induced by RSV glycoprotein G or formalin-inactivated RSV immunization. However, immunized CD1-deficient or α-GalCer-treated wild-type mice did not exhibit diminished disease following RSV challenge. Rather, some disease parameters, including cytokine production, eosinophilia, and viral clearance, were increased. These findings indicate that CD1d-dependent NK T cells play a role in expansion of CD8+ T cells and amplification of antiviral responses to RSV.

CD8+ T cells rapidly acquire NK1.1 and NK cell-associated molecules upon stimulation in vitro and in vivo.

NKT cells express both NK cell-associated markers and TCR. Classically, these NK1.1+TCRαβ+ cells have been described as being either CD4+CD8− or CD4−CD8−. Most NKT cells interact with the nonclassical MHC class I molecule CD1 through a largely invariant Vα14-Jα281 TCR chain in conjunction with either a Vβ2, -7, or -8 TCR chain. In the present study, we describe the presence of significant numbers of NK1.1+TCRαβ+ cells within lymphokine-activated killer cell cultures from wild-type C57BL/6, CD1d1−/−, and Jα281−/− mice that lack classical NKT cells. Unlike classical NKT cells, 50–60% of these NK1.1+TCRαβ+ cells express CD8 and have a diverse TCR Vβ repertoire. Purified NK1.1−CD8α+ T cells from the spleens of B6 mice, upon stimulation with IL-2, IL-4, or IL-15 in vitro, rapidly acquire surface expression of NK1.1. Many NK1.1+CD8+ T cells had also acquired expression of Ly-49 receptors and other NK cell-associated molecules. The acquisition of NK1.1 expression on CD8+ T cells was a particular property of the IL-2Rβ+ subpopulation of the CD8+ T cells. Efficient NK1.1 expression on CD8+ T cells required Lck but not Fyn. The induction of NK1.1 on CD8+ T cells was not just an in vitro phenomenon as we observed a 5-fold increase of NK1.1+CD8+ T cells in the lungs of influenza virus-infected mice. These data suggest that CD8+ T cells can acquire NK1.1 and other NK cell-associated molecules upon appropriate stimulation in vitro and in vivo.

Lipid antigen presentation in the immune system : lessons learned from CD1d knockout mice

Summary: CD I molecules represent a distinct lineage of antigen‐presenting molecules chat are evolutionarily related to the classical major histocompatility complex (MHC) dass I and class II molecules, Unlike the classical MHC products that bind peptides, GDI molecules have evolved Co bind lipids and glycolipids, Murine and human CD Id molecules can present glycolipid antigens such as α‐galactosylceramide (α‐GalCer) to CD 1d‐restricced natural killer (NK) T cells. Using CD 1d knockout mice we demonstrated chat CDI d expression is required for the development of NK T cells. These animals were also deficient in the rapid production of inter‐leukin‐4 and intcrferon‐γ in response to stimulation by anti‐CD3 antibodies. Despite these defects, CD Id knockout animals were able to generate strong T‐helper type 1 (TH1) and TH2 responses. Spleen cells from these animals neither proliferated nor produced cytokines in response to stimulation by α‐GalCer, Repeated injection of α‐GalCer into wild‐type but not CD 1 d mutant mice was able to clear metastatic tumors. We further showed that α‐GalCer can inhibit disease in diabetes‐prone non‐obese diabetic mice. Collectively, these findings with CD ld knockout animals indicate a critical role for CD 1 d‐dependent T cells in various disease conditions, and suggest that α‐GalCer may be useful for therapeutic intervention in these diseases.

Immunoregulatory Role of CD1d in the Hydrocarbon Oil-Induced Model of Lupus Nephritis

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that is accompanied by the emergence of autoreactive T cells and a reduction in regulatory T cells. Humans and mice with SLE have reduced numbers of CD1d-restricted NK T cells, suggesting a role for these cells in the regulation of SLE. In this study, we show that CD1d deficiency exacerbates lupus nephritis induced by the hydrocarbon oil pristane. This exacerbation in disease is associated with: 1) reduced TNF-α and IL-4 production by T cells, especially during the disease induction phase; and 2) expansion of marginal zone B cells. Strikingly, inoculation of pristane in wild-type mice resulted in reduced numbers and/or functions of NK T cells and CD1d-expressing dendritic cells. These findings suggest that CD1d may play an immunoregulatory role in the development of lupus in the pristane-induced model.

CD1d deficiency exacerbates inflammatory dermatitis in MRL-lpr/lpr mice.

Mechanisms responsible for the development of autoimmune skin disease in humans and animal models with lupus remain poorly understood. In this study, we have investigated the role of CD1d, an antigen‐presenting molecule known to activate natural killer T cells, in the development of inflammatory dermatitis in lupus‐susceptible MRL‐lpr/lpr mice. In particular, we have establishedMRL‐lpr/lpr mice carrying a germ‐line deletion of the CD1d genes. We demonstrate that CD1d‐deficient MRL‐lpr/lpr mice, as compared with wild‐type littermates, have more frequent and more severe skin disease, with increased local infiltration with mast cells, lymphocytes and dendritic cells, including Langerhans cells. CD1d‐deficient MRL‐lpr/lpr mice had increased prevalence of CD4+ T cells in the spleen and liver and of TCRαu2009βu2009+B220+ cells in lymph nodes. Furthermore, CD1d deficiency was associated with decreased T cell production of type 2 cytokines and increased or unchanged type 1 cytokines. These findings indicate a regulatory role of CD1d in inflammatory dermatitis. Understanding the mechanisms by which CD1d deficiency results in splenic T cell expansion and cytokine alterations, with increased dermal infiltration of dendritic cells and lymphocytes in MRL‐lpr/lpr mice, will have implications for the pathogenesis of inflammatory skin diseases.