Use of the A(2A) adenosine receptor as a physiological immunosuppressor and to engineer inflammation in vivo

Inflammation must be inhibited in order to treat, e.g., sepsis or autoimmune diseases or must be selectively enhanced to improve, for example, immunotherapies of tumors or the development of vaccines. Predictable enhancement of inflammation depends upon the knowledge of the "natural" pathways by which it is down-regulated in vivo. Extracellular adenosine and A(2A) adenosine (purinergic) receptors were identified recently as anti-inflammatory signals and as sensors of excessive inflammatory tissue damage, respectively (Ohta A and Sitkovsky M, Nature 2001;414:916-20). These molecules may function as an important part of a physiological "metabolic switch" mechanism, whereby the inflammatory stimuli-produced local tissue damage and hypoxia cause adenosine accumulation and signaling through cyclic AMP-elevating A(2A) adenosine receptors in a delayed negative feedback manner. Patterns of A(2A) receptor expression are activation- and differentiation-dependent, thereby allowing for the "acquisition" of an immunosuppressive "OFF button" and creation of a time-window for immunomodulation. Identification of A(2A) adenosine receptors as "natural" brakes of inflammation provided a useful framework for understanding how tissues regulate inflammation and how to enhance or decrease (engineer) inflammation by targeting this endogenous anti-inflammatory pathway. These findings point to the need of more detailed testing of anti-inflammatory agonists of A(2A) receptors and create a previously unrecognized strategy to enhance inflammation and targeted tissue damage by using antagonists of A(2A) receptors. It is important to further identify the contributions of different types of immune cells at different stages of the inflammatory processes in different tissues to enable the "tailored" treatments with drugs that modulate the signaling through A(2A) purinergic receptors.     

Slowly getting a clue on CD95 ligand biology

Since the ligand for the death factor CD95 (CD95L) was identified almost a decade ago, it has been established that this molecule (CD95L, FasL, Apo-1L, CD178, TNFSF6, APT1LG1) has multiple immunoregulatory and pathophysiologically relevant functions. CD95L does not only act as a death factor when externalized with secretory lysosomes on cytotoxic T and NK cells or when expressed on CD4(+) T cells in the course of activation-induced cell death, it is also a key molecule for the establishment of immune privilege or tumor cell survival and may serve as a costimulatory molecule during T cell activation. Moreover, alterations of expression or shedding of different forms of CD95L are associated with many diseases including various malignancies, HIV infection, autoimmune disorders (systemic lupus erythematodes, rheumatoid arthritis), acute myocardial infarction, traumatic injury and many others. In most cases, however, the physiological link between altered CD95L expression and pathophysiology is unknown. Given the potency of the molecule to regulate death and survival of many different cell types, the control of CD95L production, transport, storage, shedding and release is of tremendous biological and clinical interest. This commentary aims at briefly summarizing the current knowledge, hypotheses and controversies about CD95L as a multifunctional ligand and receptor. It touches upon the complex networks of intracellular dynamics of protein transport and trafficking and the potential bidirectional signal transduction capacity of CD95L with a focus on molecular interactions that have been worked out over the past years.     

Complex expression patterns of lymphocyte-specific genes during the development of cartilaginous fish implicate unique lymphoid tissues in generating an immune repertoire

Cartilaginous fish express canonical B and T cell recognition genes, but their lymphoid organs and lymphocyte development have been poorly defined. Here, the expression of Ig, TCR, recombination-activating gene (Rag)-1 and terminal deoxynucleosidase (TdT) genes has been used to identify roles of various lymphoid tissues throughout development in the cartilaginous fish, Raja eglanteria (clearnose skate). In embryogenesis, Ig and TCR genes are sharply up-regulated at 8 weeks of development. At this stage TCR and TdT expression is limited to the thymus; later, TCR gene expression appears in peripheral sites in hatchlings and adults, suggesting that the thymus is a source of T cells as in mammals. B cell gene expression indicates more complex roles for the spleen and two special organs of cartilaginous fish-the Leydig and epigonal (gonad-associated) organs. In the adult, the Leydig organ is the site of the highest IgM and IgX expression. However, the spleen is the first site of IgM expression, while IgX is expressed first in gonad, liver, Leydig and even thymus. Distinctive spatiotemporal patterns of Ig light chain gene expression also are seen. A subset of Ig genes is pre-rearranged in the germline of the cartilaginous fish, making expression possible without rearrangement. To assess whether this allows differential developmental regulation, IgM and IgX heavy chain cDNA sequences from specific tissues and developmental stages have been compared with known germline-joined genomic sequences. Both non-productively rearranged genes and germline-joined genes are transcribed in the embryo and hatchling, but not in the adult.     

Large granular lymphocyte leukaemia is characterized by a clonal T-cell receptor rearrangement in both memory and effector CD8(+) lymphocyte populations

Large granular lymphocyte (LGL) leukaemia is a disease with increased numbers of circulating granular lymphocytes and an increased percentage of clonally rearranged CD8(+)CD57(+) cells. To determine whether LGL cells are also found in other lymphocyte subsets, CD8(+) cells from 10 LGL patients were sorted into CD57(+) and CD57(-) fractions and analysed for clonality using a T-cell receptor gamma (TCR gamma) polymerase chain reaction (PCR). In nine patients, a clonal TCR rearrangement was identified in the CD8(+)CD57(+) cells, and in one patient, the TCR rearrangement was oligoclonal in the CD8(+)CD57(+) fraction. In eight out of nine of the clonally rearranged patients, the same band was also present in the CD8(+)CD57(-) fraction. To define the relationship between CD57(-) and CD57(+) LGL populations, CD8(+)CD57(-) and CD8(+)CD57(+) cells were sorted from five patients and cultured in the presence of anti-CD3 plus CD28 antibodies. The CD57(+) cells died of apoptosis before d 7, while the CD57(-) cells proliferated and differentiated into CD57(+) cells. Clonal analysis identified the same band in both cultured subpopulations and in the uncultured CD8(+) cells. Immunophenotypical analysis showed that CD8(+)CD57(-) cells expressed memory cell markers, while the CD8(+)CD57(+) cells exhibited effector characteristics. These results suggest that LGL disease originates in a CD57(-) memory T-cell compartment that continually generates CD57(+) (effector cell) progeny.     

Vaccination with a CDR2 BV6S2/6S5 peptide in adjuvant induces peptide-specific T-cell responses in patients with multiple sclerosis

Earlier studies from several groups including ours have documented that patients with multiple sclerosis (MS) have over-expression of activated T-cells from specific TCR V beta families, including BV6S2/S5 (Kotzin et al. [1991] Proc. Natl. Acad. Sci. USA 88:9161--9165; Gold et al. [1997] J. Neuroimmunol. 76:29--38). It has also been established in the rat EAE model that peptide vaccines to the over-expressed V beta 8.2 TCR can prevent MBP induced disease (Vandenbark et al. [1989] Nature 341:541--544). In the current clinical study, 10 patients were vaccinated with 300 microg of BV6S2/6S5 peptide emulsified in incomplete Freund's adjuvant (IFA) and monitored for safety and immunogenicity in a 48-week multicenter, open-label trial. The peptide vaccine was well tolerated and no serious adverse events were observed. Vaccinations induced cell-mediated immunity to the immunizing peptide in eight of 10 patients as demonstrated by lymphocyte proliferation assay (LPA) and delayed-type hypersensitivity (DTH) skin test responses. In summary, these results demonstrate that immunization with TCR BV6S2/6S5 peptide vaccine in MS patients is safe and immunogenic, and supports a larger double-blind placebo controlled trial to determine the clinical efficacy of this approach.     

Murine gamma-herpesvirus infection causes V(beta)4-specific CDR3-restricted clonal expansions within CD8(+) peripheral blood T lymphocytes

Infection of mice with the gamma-herpesvirus MHV-68 results in lytic infection in the lung cleared by CD8(+) cells and establishment of lifelong latency. An Epstein-Barr virus (EBV)-like infectious mononucleosis (IM) syndrome emerges approximately 3 weeks after infection. In human IM, the majority of T cells in the peripheral blood are monoclonal or oligoclonal and are frequently specific for lytic or latent viral epitopes. However, a unique feature of MHV-68-induced IM is a prominent MHC haplotype-independent expansion of CD8(+) T cells, the majority of which utilize V(beta)4 chains in their alphabetaTCR. The ligand driving the V(beta)4 expansion is unknown, but the V(beta) bias and MHC haplotype independence raised the possibility that these cells were responding to a virally encoded or a virally induced endogenous superantigen (sAg). The aim of this study was to determine whether this rapidly proliferating subset is composed of polyclonally or clonally expanded T cells. Complementarity-determining region (CDR)-3 size analysis of V(beta)4(+)CD8(+) cells in infected mice demonstrated CDR3-restricted expansions in the V(beta)4 family as a whole. More refined analysis demonstrated major distortions in every J(beta) subfamily. V-D-J junctional region sequencing indicated that these CDR3 size-restricted expansions were composed of clonal or oligoclonal populations. The sequences were largely unique in individual mice, although evidence for 'public' or highly conserved T cell expansions was also seen between different mice. Taken together with previous studies showing an apparent MHC independence, the data suggest that a novel ligand, distinct from conventional sAg and peptide-MHC, drives proliferation of V(beta)4(+)CD8(+) T cells.     

电离辐射对T淋巴细胞IL-2分泌和细胞毒活性的影响

正常人外周血单个核细胞（ＰＢＭＣ）体外经１～６Ｇｙγ射线照射后，间接免疫荧光法分析受照Ｔ细胞Ｔ细胞抗原受体（ＴＣＲ）、ＣＤ＿３及ＣＤ＿（２３）阳性细胞百分率，Ｈ￣３－ＴｄＲ掺入及释放法测定白细胞介素－２（ＩＬ－２）分泌及Ｔ细胞细胞毒活性，免疫细胞化学法分析Ｔ细胞内ＴＣＲ及ＣＤ＿３表达．结果表明，Ｔ细胞ＴＣＲ、ＣＤ．及ＣＤ＿（２５）表达及ＩＬ－２分泌和细胞毒活性皆呈照射剂量依赖性降低．受照Ｔ细胞ＩＬ－２分泌及细胞毒活性抑制在一定程度上与细胞表面ＴＣＲ、ＣＤ＿３及ＣＤ＿（２５）表达减少、活性损伤有关，而细胞表面ＴＣＲ和ＣＤ＿３表达降低可能与大量ＴＣＲ及ＣＤ＿３在受照细胞胞浆内堆积有关．     

小鼠CD^3＋TCRαβ^＋CD^—CD8^—胸腺细胞特性分析

目的：分析CD^3 TCRαβ^ CD^-CD8^-胸腺细胞的特性，推断其在胸腺发育中表型和功能的成熟过程。方法：分离纯化小鼠胸腺DN细胞，用多重染色的方法分析CD^3 TCRαβ^ CD^-CD8^-细胞的表型和TCR库，并与外周淋巴结的相应细胞进行对比。结果：DNA胸腺细胞为异质性细胞，包括CD3^-DN细胞和CD3^ DN细胞，而CD3^ DN细胞又分为CD^3 TCRαβ^ 和CD3^ TCRγδ^ 2个亚群。其中，CD^3 TCRαβ^ DN细胞体积较小，绝大部分细胞对可的松耐受，细胞中能与自身反应的Vβ^3 和Vβ11^ 细胞比例极低，表型较为成熟，与髓质型SP（single positive) 细胞相似。结论：CD^3 TCRαβ^ DN细胞不同于CD^3 TCRαβ^－DN细胞，是一个独特的细胞亚群，只有在经历表型和功能的进一步成熟才能迁出胸腺，移至外周。