CD1-Restricted T cells: T cells with a unique immunological niche

Intricate Relationship Between Adaptive and Innate Immune System in Allergic Contact Dermatitis

Allergic contact dermatitis (ACD) is a complex immunological allergic disease characterized by the interplay between the innate and adaptive immune system. Initially, the role of the innate immune system was believed to be confined to the initial sensitization phase, while adaptive immune reactions were linked with the advanced elicitation phase. However, recent data predicted a comparatively mixed and interdependent role of both immune systems throughout the disease progression. Therefore, the actual mechanisms of disease progression are more complex and interlinked. The aim of this review is to combine such findings that enhanced our understanding of the pathomechanisms of ACD. Here, we focused on the main cell types from both immune domains, which are involved in ACD, such as CD4+ and CD8+ T cells, B cells, neutrophils, and innate lymphoid cells (ILCs). Such insights can be useful for devising future therapeutic interventions for ACD.

Possible Immune Regulation of Natural Killer T Cells in a Murine Model of Metal Ion-Induced Allergic Contact Dermatitis

Metal often causes delayed-type hypersensitivity reactions, which are possibly mediated by accumulating T cells in the inflamed skin, called irritant or allergic contact dermatitis. However, accumulating T cells during development of a metal allergy are poorly characterized because a suitable animal model is unavailable. We have previously established novel murine models of metal allergy and found accumulation of both metal-specific T cells and natural killer (NK) T cells in the inflamed skin. In our novel models of metal allergy, skin hypersensitivity responses were induced through repeated sensitizations by administration of metal chloride and lipopolysaccharide into the mouse groin followed by metal chloride challenge in the footpad. These models enabled us to investigate the precise mechanisms of the immune responses of metal allergy in the inflamed skin. In this review, we summarize the immune responses in several murine models of metal allergy and describe which antigen-specific responses occur in the inflamed skin during allergic contact dermatitis in terms of the T cell receptor. In addition, we consider the immune regulation of accumulated NK T cells in metal ion-induced allergic contact dermatitis.

Natural killer T cells: an unconventional T-cell subset with diverse effector and regulatory functions

Natural killer T (NKT) cells are a unique subset of lymphocytes that express NK cell markers such as CD161 and CD94, as well as a T-cell receptor (TCR) alpha/beta, with a restricted repertoire, which distinguishes them from NK cells, which lack a TCR. In contrast to conventional T-lymphocytes, the TCR of NKT cells does not interact with that of peptide antigens presented by classical major histocompatibility complex-encoded class I or II molecules. Instead, this TCR recognizes glycolipids presented by CD1d, a non-classical antigen-presenting molecule. The rapid response of NKT cells to their cognate antigens is characteristic of an innate immune response, and allows the polarizing cytokines (IFN-gamma and/or IL-4) to regulate adaptive immunity. NKT cells have been found to be critical in the immune response against viral infections and malaria, as well as in tumor immunity, and certain autoimmune diseases. NKT cells have been assessed to represent the "trait d'union" between innate and adaptive immunity. They play an active role in skin diseases, such as contact sensitivity, which have been implicated in UV-induced immunosuppression and psoriasis. Thus, NKT-cells are emerging as an important subset of lymphocytes, with a protective role in host defense and a pathogenic role in certain immune-mediated disease states.

Human natural killer T cells infiltrate into the skin at elicitation sites of allergic contact dermatitis

The purpose of this study is to identify invariant natural killer T cells (NKT cells) in cellular infiltrate of human allergic contact dermatitis (ACD) skin challenge sites. Skin biopsy specimens were taken from positive patch test reactions from 10 different patients (9 different allergens) and studied by immunochemistry, real-time PCR, nested PCR, and in situ hybridization to identify NKT cells and the cytokines associated with this cell type. Invariant NKT cells were identified in all the 10 skin biopsy specimens studied, ranging from 1.72 to 33% of the cellular infiltrate. These NKT cells were activated in all cases, as they expressed cytokine transcripts for IFN-gamma and IL-4. Invariant NKT cells are present in ACD, regardless of the allergen that triggers the reaction, and are in an activated state. We conclude that innate immunity plays a role in late phases of type IV hypersensitivity reactions and may be responding to self-lipids released during allergic inflammation. These data complement the previous work by other investigators that suggest that NKT cells are important in the early cellular response during primary immune responses to allergens. Herein, it is demonstrated that NKT cells are constantly present during the late elicitation phase of human type IV hypersensitivity reactions.

Ceramide-Dependent Regulation of Human Epidermal Keratinocyte CD1d Expression during Terminal Differentiation

Human keratinocytes (KC), when cultured under conditions to remain undifferentiated or to terminally differentiate, changed their cellular distribution of CD1d. As studied by confocal microscopy, undifferentiated KC had a pool of cytoplasmic CD1d, whereas after terminal differentiation, this molecule localized in the cell membrane, which recapitulates CD1d expression in vivo. A comparison of undifferentiated and differentiated cultured KC did not reveal any differences in the association with beta(2)-microglobulin, invariant chain of class II MHC, or patterns of glycosylation, suggesting that these biochemical properties are not regulating the cellular distribution of CD1d. Time-course studies of CD1d gene expression indicated that KC slowly increased gene expression with CaCl(2)-induced terminal differentiation. Increased CD1d gene expression was dependent on ceramide synthesis, because fumonisin B1, a ceramide synthetase inhibitor, blocked the increase in CD1d gene expression during terminal differentiation. Similarly, exogenous ceramide or the ceramidase inhibitor, B13, induced CD1d gene expression by undifferentiated, but not terminally differentiated, KC. A protein kinase C-zeta (PKC-zeta) inhibitor (a pseudosubstrate oligopeptide), but not a PKC-alphabeta inhibitor, significantly decreased CD1d gene expression by undifferentiated or ceramide-stimulated cultured, undifferentiated KC. As expected, downstream signaling events of PKC-zeta (JNK phosphorylation and NF-kappaBeta accumulation in the nucleus) were also attenuated. The calcineurin phosphatase inhibitor cyclosporine A, which blocks KC terminal differentiation, also blocked CD1d gene expression by cultured KC. In conclusion, this novel function of cellular ceramides extends the importance of this class of biologically active lipids beyond that of terminal differentiation and barrier function in normal human skin.

Role of CD1d in coxsackievirus B3-induced myocarditis

The myocarditic (H3) variant of Coxsackievirus B3 (CVB3) causes severe myocarditis in BALB/c mice and BALB/c mice lacking the invariant J alpha 281 gene, but minimal disease in BALB/c CD1d(-/-) animals. This indicates that CD1d expression is important in this disease but does not involve the invariant NKT cell often associated with CD1d-restricted immunity. The H3 variant of the virus increases CD1d expression in vitro in neonatal cardiac myocytes whereas a nonmyocarditic (H310A1) variant does not. V gamma 4(+) T cells show increased activation in both H3-infected BALB/c and J alpha 281(-/-) mice compared with CD1d(-/-) animals. The activated BALB/c V gamma 4(+) T cells from H3-infected mice kill H3-infected BALB/c myocytes and cytotoxicity is blocked with anti-CD1d but not with anti-MHC class I (K(d)/D(d)) or class II (IA/IE) mAbs. In contrast, H3 virus-infected CD1d(-/-) myocytes are not killed. These studies demonstrate that CD1d expression is essential for pathogenicity of CVB3-induced myocarditis, that CD1d expression is increased early after infection in vivo in CD1d(+) mice infected with the myocarditic but not with the nonmyocarditic CVB3 variant, and that V gamma 4(+) T cells, which are known to promote myocarditis susceptibility, appear to recognize CD1d expressed by CVB3-infected myocytes.

Vgamma4(+) T cells promote autoimmune CD8(+) cytolytic T-lymphocyte activation in coxsackievirus B3-induced myocarditis in mice: role for CD4(+) Th1 cells

T cells expressing the Vgamma4 T-cell receptor (TCR) promote myocarditis in coxsackievirus B3 (CVB3)-infected BALB/c mice. CD1, a major histocompatibility complex (MHC) class I-like molecule, is required for activation of Vgamma4(+) cells. Once activated, Vgamma4(+) cells initiate myocarditis through gamma interferon (IFN-gamma)-mediated induction of CD4(+) T helper type 1 (Th1) cells in the infected animal. These CD4(+) Th1 cells are required for activation of an autoimmune CD8(+) alphabeta TCR(+) effector, which is the predominant pathogenic agent in this model of CVB3-induced myocarditis. Activated Vgamma4(+) cells can adoptively transfer myocarditis into BALB/c mice infected with a nonmyocarditic variant of CVB3 (H310A1) but cannot transfer myocarditis into either uninfected or CD1(-/-) recipients, demonstrating the need for both infection and CD1 expression for Vgamma4(+) cell function. In contrast, CD8(+) alphabeta TCR(+) cells transfer myocarditis into either infected CD1(-/-) or uninfected recipients, showing that once activated, the CD8(+) alphabeta TCR(+) effectors function independently of both virus and CD1. Vgamma4(+) cells given to mice lacking CD4(+) T cells minimally activate the CD8(+) alphabeta TCR(+) cells. These studies show that Vgamma4(+) cells determine CVB3 pathogenicity by their ability to influence both the CD4(+) and CD8(+) adaptive immune response. Vgamma4(+) cells enhance CD4(+) Th1 (IFN-gamma(+)) cell activation through IFN-gamma- and CD1-dependent mechanisms. CD4(+) Th1 cells promote activation of the autoimmune CD8(+) alphabeta TCR(+) effectors.

Medical care from childhood to adulthood in type 1 and type 2 diabetes

Diabetes mellitus comprises a heterogeneous group of diseases that have in common the development of macro- and microvascular complications. It is now possible to identify subjects at high risk of Type 1 or Type 2 diabetes, especially in the patient's family members. Preventive interventions are quickly becoming available, and can help delay the onset of the disease and thereby reduce complications in these subjects. Furthermore the correct etiological diagnosis of diabetes is fundamental in providing the best treatment for the patient. Maturity-onset diabetes of the young (MODY) syndrome should be suspected in cases of a subtle onset of diabetes and autosomal dominant inheritance. Mitochondrial DNA mutations should be considered when a diabetic patient also suffers from deafness or if there is a family history of this combination in the mother side of the family. Atypical diabetes has to be identified by the physician to avoid mistakes when the patient enters the non-insulin-dependent phase. In the case of Wolfram's syndrome a gene analysis for each family member should be performed to identify heterozygote subjects. Recently, many discoveries in genetics help us better understand the pathogenesis of the diseases and diagnose the monogenic form of diabetes more easily. If all family members are followed in the same center, clues from the family history are readily available for differential diagnosis and preventive interventions can be established more effectively.