Regulatory T-cell functions are subverted and converted owing to attenuated Foxp3 expression

The naturally occurring regulatory T cell (T(r)) is the pivotal cell type that maintains self-tolerance and exerts active immune suppression. The development and function of T(r) cells is controlled by Foxp3 (refs 1, 2), a lack of which results in loss of T(r) cells and massive multi-organ autoimmunity in scurfy mice and IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) patients. It is generally thought that, through a binary mechanism, Foxp3 expression serves as an on-and-off switch to regulate positively the physiology of T(r) cells; however, emerging evidence associates decreased Foxp3 expression in T(r) cells with various immune disorders. We hypothesized that Foxp3 regulates T(r) cell development and function in a dose-dependent, non-binary manner, and that decreased Foxp3 expression can cause immune disease. Here, by generating a mouse model in which endogenous Foxp3 gene expression is attenuated in T(r) cells, we show that decreased Foxp3 expression results in the development of an aggressive autoimmune syndrome similar to that of scurfy mice, but does not affect thymic development, homeostatic expansion/maintenance or transforming-growth-factor-beta-induced de novo generation of Foxp3-expressing cells. The immune-suppressive activities of T cells with attenuated Foxp3 expression were nearly abolished in vitro and in vivo, whereas their anergic properties in vitro were maintained. This was accompanied by decreased expression of T(r) cell 'signature genes'. Notably, T cells expressing decreased Foxp3 preferentially became T-helper 2 (T(h)2)-type effectors even in a T(h)1-polarizing environment. These cells instructed T(h)2 differentiation of conventional T cells, which contributed to the immune diseases observed in these mice. Thus, decreased Foxp3 expression causes immune disease by subverting the suppressive function of T(r) cells and converting T(r) cells into effector cells; these findings are important for understanding the regulation of T(r) cell function and the aetiology of various human immune diseases.     

Mast cells are essential intermediaries in regulatory T-cell tolerance

Contrary to the proinflammatory role of mast cells in allergic disorders, the results obtained in this study establish that mast cells are essential in CD4+CD25+Foxp3+ regulatory T (T(Reg))-cell-dependent peripheral tolerance. Here we confirm that tolerant allografts, which are sustained owing to the immunosuppressive effects of T(Reg) cells, acquire a unique genetic signature dominated by the expression of mast-cell-gene products. We also show that mast cells are crucial for allograft tolerance, through the inability to induce tolerance in mast-cell-deficient mice. High levels of interleukin (IL)-9--a mast cell growth and activation factor--are produced by activated T(Reg) cells, and IL-9 production seems important in mast cell recruitment to, and activation in, tolerant tissue. Our data indicate that IL-9 represents the functional link through which activated T(Reg) cells recruit and activate mast cells to mediate regional immune suppression, because neutralization of IL-9 greatly accelerates allograft rejection in tolerant mice. Finally, immunohistochemical analysis clearly demonstrates the existence of this novel T(Reg)-IL-9-mast cell relationship within tolerant allografts.     

Amplification of a gene coding for human T-cell differentiation antigen

Using previously isolated mouse L-cell transferents for the human T-cell differentiation antigen Leu-2, we now report the first example of spontaneous gene amplification for membrane antigens. The Leu-2 (or T8) antigen is normally expressed on T lymphocytes that have cytotoxic or suppressor functions. Cells of a Leu-2 transfected clone were stained with fluorescein-tagged monoclonal anti-Leu-2, and the brightest 0.1-0.3% of cells were viably separated using a fluorescence activated cell sorter (FACS). After growth of these selected cells, sorting and regrowth was repeated six times, resulting in a population of cells that, compared with the starting population, stains 40 times brighter for Leu-2 and whose DNA transforms 20 times more efficiently for Leu-2. In addition, these cells have 10- to 50-fold amplified human DNA sequences and numerous double minute chromosome fragments, a common indicator of gene amplication in mouse cells.     

A new T-cell receptor gene located within the alpha locus and expressed early in T-cell differentiation

A new T-cell receptor gene lies just 5' to the J alpha C alpha coding regions. Its placement in this location suggests a novel mechanism for the regulation of expression of one T-cell receptor polypeptide to another during ontogeny. Rearrangement of this locus occurs very early in thymic differentiation and its RNA expression parallels that of the gamma-chain in thymic subpopulations, making this a possible candidate for the recently described delta-chain of the T-cell receptor.     

An excitable gene regulatory circuit induces transient cellular differentiation

Certain types of cellular differentiation are probabilistic and transient. In such systems individual cells can switch to an alternative state and, after some time, switch back again. In Bacillus subtilis, competence is an example of such a transiently differentiated state associated with the capability for DNA uptake from the environment. Individual genes and proteins underlying differentiation into the competent state have been identified, but it has been unclear how these genes interact dynamically in individual cells to control both spontaneous entry into competence and return to vegetative growth. Here we show that this behaviour can be understood in terms of excitability in the underlying genetic circuit. Using quantitative fluorescence time-lapse microscopy, we directly observed the activities of multiple circuit components simultaneously in individual cells, and analysed the resulting data in terms of a mathematical model. We find that an excitable core module containing positive and negative feedback loops can explain both entry into, and exit from, the competent state. We further tested this model by analysing initiation in sister cells, and by re-engineering the gene circuit to specifically block exit. Excitable dynamics driven by noise naturally generate stochastic and transient responses, thereby providing an ideal mechanism for competence regulation.     

Association of the T-cell regulatory gene CTLA4 with susceptibility to autoimmune disease

Genes and mechanisms involved in common complex diseases, such as the autoimmune disorders that affect approximately 5% of the population, remain obscure. Here we identify polymorphisms of the cytotoxic T lymphocyte antigen 4 gene (CTLA4)--which encodes a vital negative regulatory molecule of the immune system--as candidates for primary determinants of risk of the common autoimmune disorders Graves' disease, autoimmune hypothyroidism and type 1 diabetes. In humans, disease susceptibility was mapped to a non-coding 6.1 kb 3' region of CTLA4, the common allelic variation of which was correlated with lower messenger RNA levels of the soluble alternative splice form of CTLA4. In the mouse model of type 1 diabetes, susceptibility was also associated with variation in CTLA-4 gene splicing with reduced production of a splice form encoding a molecule lacking the CD80/CD86 ligand-binding domain. Genetic mapping of variants conferring a small disease risk can identify pathways in complex disorders, as exemplified by our discovery of inherited, quantitative alterations of CTLA4 contributing to autoimmune tissue destruction.     

Presence of T-cell receptor mRNA in functionally distinct T cells and elevation during intrathymic differentiation

Understanding the differentiation of functionally distinct subsets of T lymphocytes is essential to unravel their crucial role in the immune response and awaits knowledge of the assembly and expression of genes encoding the T-cell receptor. Recently, we have cloned and sequenced complementary DNA that may specify part of the human T-cell receptor. The deduced protein sequence showed extensive similarity to the entire length of mammalian immunoglobulin light chains. In addition, sequences corresponding to this message undergo somatic rearrangements and are assembled from non-contiguous genomic sequences into a single mRNA molecule, a mechanism similar to those found in the generation of immunoglobulin messages. A related molecule from the mouse was also isolated independently by Hedrick et al. Here we show that the putative T-cell receptor mRNA is expressed at a relatively high level during intrathymic differentiation before decreasing about 10-20-fold in normal, mature peripheral blood T cells and that it can also be detected in T-cell clones with helper and cytotoxic functions, as well as in at least one clone with suppressor properties.     

Serum beta 2-microglobulin binds to a T-cell differentiation antigen and increases its expression

The human T-cell leukaemia and differentiation antigen HTA 1 is defined by the monoclonal antibody NA1/34 (ref. 1) and also recognized by the monoclonal antibody OKT6. Like class I products of the human major histocompatibility complex, it has a glycosylated heavy (alpha) chain of approximately 45-50,000 molecular weight (MW) in non-covalent association with beta 2-microglobulin (beta 2m) (MW 11,900). A particular feature of HTA 1 is the presence in significant amounts of an additional beta 2m-like subunit, called beta t (refs 3, 4). Top facilitate biochemical studies we have prepared a high HTA 1 expressor variant (NH17) of the human thymoma line MOLT-4. The N-terminal amino acid sequence of the beta t purified from this cell line was shown to be indistinguishable from that of bovine beta 2m. Further, beta t was present when the cells were grown in medium containing fetal calf serum (FCS), but absent from cells grown with human serum (HuS). We show here that addition of human and bovine beta 2m to MOLT-4 and NH17 cells grown in serum-free medium produces a significant elevation of HTA 1 antigen expression, providing evidence for a regulatory or stabilizing function for the exchange of extracellular beta 2m with a cell-surface antigen.     

Abrogation of oral tolerance by contrasuppressor T cells suggests the presence of regulatory T-cell networks in the mucosal immune system

Continuous ingestion of a thymus-dependent (TD) antigen differentially affects two compartments of the immune system. A secretory IgA antibody response is induced in mucosal tissues, concurrent with a state of antigen-specific systemic unresponsiveness to parenteral challenge, termed oral tolerance. The precise mechanisms whereby gut antigenic exposure induces oral tolerance are unknown, although T-suppressor cells, anti-idiotypic networks and immune complex formation have all been proposed. Here we show that the systemic unresponsiveness of mice made orally tolerant to the TD antigen sheep red blood cells (SRBC) is reversed by the adoptive transfer of Lyt-1+,2-, Vicia villosa lectin-adherent and I-J+ T cells derived from mice which are genetically resistant to the induction of oral tolerance to SRBC. This T-cell subpopulation has the characteristics of contrasuppressor effector T cells (Tcs). Small numbers of these Tcs cells reverse SRBC-specific tolerance both in vivo and in vitro. This finding offers new insight into the mechanisms of oral tolerance induction and maintenance, and suggests that a network of T cells are involved in the regulation of host responses to ingested antigens.     

木犀草素抑制3T3-L1前脂肪细胞的分化

为研究木犀草素在3T3-L1前脂肪细胞成脂分化过程中的作用,文章探讨木犀草素抑制脂质沉积的作用机制,选取3T3-L1前脂肪细胞作为研究对象,在其分化过程中添加木犀草素,利用噻唑蓝(MTT)实验研究木犀草素对3T3-L1增殖的作用;利用油红O染色确定其对3T3-L1前脂肪细胞脂肪化的影响;利用定量聚合酶链式反应(polymerase chain reaction,PCR)检测木犀草素对3T3-L1脂肪化相关基因的表达影响。结果表明,20μmol/L的木犀草素可以降低3T3-L1细胞的脂肪化,减少脂质聚集,并且降低了3T3-L1细胞中脂肪化相关基因Pparγ、C/EBPα、Ap2和Fas等基因的表达。     

CD8、Foxp3和CD1a在口腔潜在恶性病变中的表达及临床意义

目的:利用组织微阵列技术从组织学层面上探究细胞毒性T细胞(CD8),调节性T细胞(Foxp3)和树突状细胞的表面标记(CD1 a)在口腔潜在恶性病变(OPMDs)组织中的表达情况,评估CD8、Foxp3和CD1 a在人口腔黏膜上皮异常增生过程中不同阶段的表达规律及其临床意义.方法:采用免疫组织化学染色(IHC)技术检测...