CXCL16 influences the nature and specificity of CpG-induced immune activation

Unmethylated CpG motifs are present at high frequency in bacterial DNA. They provide a danger signal to the mammalian immune system that triggers a protective immune response characterized by the production of Th1 and proinflammatory cytokines and chemokines. Although the recognition of CpG DNA by B cells and plasmacytoid dendritic cells is mediated by TLR 9, these cell types differ in their ability to bind and respond to structurally distinct classes of CpG oligonucleotides. This work establishes that CXCL16, a membrane-bound scavenger receptor, influences the uptake, subcellular localization, and cytokine profile induced by D oligonucleotides. This is the first example of a surface receptor modifying the cellular specificity and nature of the immune response mediated by an intracellular TLR.     

A tumor suppressive DNA translocase named FANCM

FANCM is named after Fanconi anemia (FA) complement group M. The clinical symptoms of FA include congenital abnormalities, pancytopenia, and cancer proneness. However, recent studies reveal that biallelic inactivation of FANCM does not cause the constellation of FA symptoms, but predisposes patients to cancer and infertility. FANCM is a tumor suppressor gene that encodes a conserved and structure-specific DNA translocase. It controls the outcome of homologous recombination and facilitates DNA replication across a variety of natural and chemically induced obstacles. This review details our current understanding of FANCM as a facilitator of the cellular functions of caretaker proteins, including FA, Bloom syndrome, and Ataxia telangiectasia and RAD3-related proteins, which collectively ensure the maintenance of chromosome stability during DNA replication.     

人扁桃体中应激免疫抑制蛋白的初步观察

以前的实验证明,在应激条件下,外周淋巴组织中产生一种蛋白质,具有抑制某些免疫功能的作用,称为应激免疫抑制蛋白（immune suppressive protein of stress,ISPS）。本实验用人外周淋巴器官扁桃体进行了研究,证明扁桃体的提取物能抑制小鼠由Con A诱导的淋巴细胞转化,而且这种抑制作用可被ISPS单克隆抗体（2C4）部分翻转。间接ELISA法证明人扁桃体提取物能与2C4单克隆抗体相结合。以ISPS单克隆抗体（2C4）作免疫组织化学研究,证明人扁桃体中有很多染色呈阳性的细胞。这些结果从不同角度提示,人外周淋巴组织中存在一种与ISPS相类似的免疫抑制物质。     

The suppressive effect of continuous infusion of bilirubin on the immune response in mice

Mice (strains Balb/c and A/J) received an intravenous infusion of bilirubin for a 1 d period. The infusion was delivered at various phases of the primary reaction; the degree of the immune response was expressed as the number of antibody-forming cells against sheep erythrocytes. Bilirubin infusion during both the inductive and productive phase of the primary reaction decreased significantly the immune response. We assume that bilirubin influences the differentiation of immunocompetent cells immediately after their contact with the antigen; in addition it acts in the period of the quantitative increase of the number of antibody-producing cells.     

Accumulation of glutathione disulfide mediates NF-kappaB activation during immune stimulation with CpG DNA

Innate immune cells recognize pathogens by detecting molecular patterns that are distinct from those of the host. One such pattern is unmethylated CpG dinucleotides, which are common in bacterial DNA but not in vertebrate genomes. Macrophages respond to such CpG motifs in bacterial DNA or synthetic oligodeoxynucleotides (ODN) by inducing NF-kappaB and secreting proinflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), but the mechanisms regulating this have been unclear. CpG ODN-stimulated cells produce reactive oxygen species (ROS) and have a decreased ratio of intracellular glutathione/glutathione disulfide (GSH/GSSG), indicating a shift to a more oxidized intracellular redox state. To determine whether this may play a role in mediating the CpG-induced macrophage activation, the GSH/GSSG redox state was manipulated in the murine macrophagelike cell line RAW264.7. Treatment of cells with BCNU to inhibit glutathione reductase (GR) enhanced the CpG-induced intracellular oxidation and decreased the GSH/GSSG, with increased activation of NF-kappaB and a doubling in the CpG-induced production of IL-6 and TNF-alpha. Experimental manipulation of the intracellular GSSG concentration during inhibition of cellular prooxidant production demonstrated that increased intracellular GSSG is a primary signal that is directly or indirectly required for CpG-induced NF-kappaB activation but is not in itself sufficient to trigger this in the absence of CpG ODN. These data suggest the existence of a second CpG-induced intracellular signal, independent of GSSG, mediating the activation of innate immunity by bacterial DNA.     

Effect of tumor necrosis factor DNA on immune response to DNA immunization against herpes simplex virus

A study was made of the adjuvant effect of the mouse tumor necrosis factor alpha (mTNF alpha) on DNA immunization against the herpes simplex virus type 1 (HSV1). The HSV1 gD gene (pDNAgD) served as an immunogen; mTNF alpha or its gene cloned in an eukaryotic expression vector (pDNAmTNF) were used to modulate the immune response. Double immunization with pDNAgD led to a sixfold increase in the in vitro T-cell response, a high (1:2000) titer of anti-HSV1 antibodies (including virus-neutralizing antibodies), an increase in IgG2a/IgG1 (suggesting a shift of the immune response to the Th1 type), and no change in CD4/CD8 T-cell ratio. A single injection of mTNF alpha along with inactivated HSV1 allowed a twice higher antibody titer and a fourfold higher T-cell response as compared with immunization with HSV1 alone. Double immunization with both pDNAgD and pDNAmTNF increased the titer of anti-HSV1 antibodies and the T-cell response by factors of 8 and 1.5, respectively, as compared with immunization with pDNAgD alone. However, the protective effect was significantly lower with the two plasmids than with pDNAgD (73 vs. 100%). Thus, DNA immunization with pDNAgD induced both B- and T-cell responses and completely protected mice from a lethal doze of HSV1. The adjuvant properties of mTNF alpha and pDNAmTNF need further investigation.     

Effect of solar particle event radiation on gastrointestinal tract bacterial translocation and immune activation

Space flight conditions within the protection of Earth's gravitational field have been shown to alter immune responses, which could lead to potentially detrimental pathology. An additional risk of extended space travel outside the Earth's gravitational field is the effect of solar particle event (SPE) radiation exposure on the immune system. Organisms that could lead to infection include endogenous, latent viruses, colonizing pathogenics, and commensals, as well as exogenous microbes present in the spacecraft or other astronauts. In this report, the effect of SPE-like radiation on containment of commensal bacteria and the innate immune response induced by its breakdown was investigated at the radiation energies, doses and dose rates expected during an extravehicular excursion outside the Earth's gravitational field. A transient increase in serum lipopolysaccharide was observed 1 day after irradiation and was accompanied by an increase in acute-phase reactants and circulating proinflammatory cytokines, indicating immune activation. Baseline levels were reestablished by 5 days postirradiation. These findings suggest that astronauts exposed to SPE radiation could have impaired containment of colonizing bacteria and associated immune activation.     

Effect of H chain V region on complement activation by immobilized immune complexes.

Activation of C by immune complexes (IC) in tissues and the inflammatory consequences are major determinants in the pathogenesis of many autoimmune disorders. To assess the factors involved in C activation by such IC, we examined the binding of C components by chimeric IgG1 antibodies bound to immobilized Ag. We previously reported that alterations in the H chain V regions can affect the binding of first component of C (C1q) and a major breakdown product of the third C component (C3b) when otherwise identical antibodies were bound to immobilized (Tyr, Glu)-Ala-Lys. To evaluate C activation of these antibodies in well defined IC, we utilized a 9-amino acid peptide conjugated to BSA as Ag. The peptide:BSA conjugate was bound similarly by the two IgG1 antibodies which differed mainly in the CDR3 regions, but also in 9 other amino acids in the H chain V region. When soluble IC were prepared with the two antibodies, they activated C similarly. However, C activation by solid phase Ag:antibody complexes differed; we found that antibody 10B bound more C1q and C3b than antibody B11 did, unless the Ag was present at high density on the plates. These data suggest that the variable region differences affect C activation by these antibody when they are bound to immobilized Ag. Furthermore, these results underscore the differences in C activation by the same antibody depending upon whether the IC are free in solution or immobilized.     

Visualizing and quantifying the suppressive effects of glucocorticoids on the tadpole immune system in vivo

A challenging topic in undergraduate physiology courses is the complex interaction between the vertebrate endocrine system and the immune system. There are relatively few established and accessible laboratory exercises available to instructors to help their students gain a working understanding of these interactions. The present laboratory module was developed to show students how glucocorticoid receptor activity can be pharmacologically modulated in Xenopus laevis tadpoles and the resulting effects on thymus gland size visualized and quantified in vivo. After treating young tadpoles with a cortisol receptor agonist (dexamethasone) for 1 wk, students can easily visualize the suppressive effects of glucocorticoids on the intact thymus gland, which shrinks dramatically in size in response to this steroid hormone analog. However, the suppressive effect of dexamethasone is nullified in the presence of the glucocorticoid receptor antagonist RU-486, which powerfully illustrates the specific effects of glucocorticoid receptor inhibition on the immune system. Image analysis and statistics software are used to quantify the effects of glucocorticoid modulation on thymus size.     

Lack of suppressive activity of human primary melanoma cells on the activation of autologous lymphocytes

Summary Previous studies have indicated that primary but not metastatic melanomas were able to stimulate the proliferation of autologous (Auto) peripheral blood lymphocytes (PBL) in 73% of cases. On the other hand, 57% of the metastatic melanomas were shown to be suppressive when melanoma cells (Me) were admixed with Auto-PBL stimulated with allogeneic (Allo) PBL or interleukin 2 (IL-2) at the beginning of a 6-day incubation period. Here, we report that the suppressive activity of Me is a functional characteristic associated with a particular stage of the disease. In fact, we found that none of the 11 primary tumors tested were able to inhibit the proliferative response of Auto-PBL to Allo-PBL or IL-2 at all the doses of tumor cells used. The generation of lymphocytes cytotoxic against Auto-Me or K562 was also not inhibited. Of the 11 primary tumors checked for suppression, 8 were able to stimulate Auto-PBL in a primary mixed lymphocyte tumor culture. We conclude that opposite functions, stimulation and inhibition of autologous lymphocyte responses are characteristics of primary and metastatic Me, respectively.This work was supported in part by the Italian Association for Cancer Research (Milan) and by grants # 85.02162.44 and 86.00663.44 of the Finalized Project Oncology of CNR of Rome, Italy     

Multiple suppressive effects of transforming growth factor beta 1 on the immune response in chickens

The immunosuppressive effect of human recombinant TGF-beta 1 on chicken immune responses in vitro was evaluated. TGF-beta 1 at 1-10 ng/ml reduced T cell proliferation in response to concanavalin A by 50-80% and B cell proliferation in response to LPS by greater than 90%. In contrast, when added to immune spleen cells, it reduced the secondary PFC response to sheep erythrocytes by less than 50%, particularly when added at the same time as antigen on Day 2 of incubation. When TGF-beta 1 was added during a 2-day incubation to nylon wool-nonadherent immune or normal spleen cells, it caused the maintenance and/or appearance of suppressor cells. These suppressor cells, in coculture with immune spleen cells, inhibited the secondary PFC response in vitro without any further exposure to TGF-beta 1. The phenotype of the cells giving rise to suppressor cells under the influence of TGF-beta 1 was CT8+, TCR2+(alpha,beta), CT4-, TCR1-(gamma,delta) cells. The results suggest that, in addition to direct suppressive effects on the proliferation of B cells and of some T cells, TGF-beta 1 may suppress immune responses by maintaining or by promoting the development of suppressor T cells.     

Different susceptibility of various immune reactions to suppressive effect in the tumor-bearing state

Summary Suppression of various types of immune reactions including antibody (Ab) production, cell-mediated cytolysis (CMC), and delayed footpad reaction (DFR) was compared in EL-4 lymphoma-bearing syngeneic mice. In the primary response, the suppression of Ab production and CMC was detected 4 days after tumor inoculation, reached a peak on day 8, and then disappeared. The suppression of DFR was detected on day 1 and persisted to day 12. The suppressive effects of tumor-bearing mice could be transferred with sera to normal recipients, and the degree of the suppressive effect in tumor-bearing hosts correlated with the suppressive effect of sera but not with tumor size. In the secondary response, the suppressive effect of the tumor-bearing state was detected only on DFR. Spleen cells of these hosts were able to transfer positive DFR adoptively to normal recipients, indicating the presence of sensitized lymphocytes in the absence of expression. DFR of normal mice in the primary response was suppressed by transfer of sera of tumor-bearing mice befor elicitation, at which time sensitized lymphocytes should already have been raised. The very high susceptibility of DFR to the suppressive effects of the tumor-bearing state may be ascribed to the distinct susceptibility of mononuclear cells, probably of the macrophage series, which are required as secondary cells for expression of DFR. Further studies with Sephadex G-200 fractionation of the sera from the tumor-bearing mice showed that the immunosuppressive activity appeared in the initial fraction containing relatively high-molecular-weight materials.     

Selective suppressive effects of glucocorticoids on the early events in the human B cell activation process

The effect of hydrocortisone on the induction of human B cell activation and proliferation has been described. Hydrocortisone prevents the anti-mu-induced cell enlargement of small tonsillar B cells, blocks expression of the activation markers 4F2 and 5E9 induced by anti-mu, inhibits RNA synthesis of small B cells stimulated by anti-mu with or without BCGF, and suppresses B cell proliferation in response to anti-mu and BCGF or to Staphylococcus aureus Cowan I. In contrast, hydrocortisone does not affect the proliferative response of in vitro or in vivo preactivated B cells. Therefore, hydrocortisone has a selective inhibitory effect on early events in the human B cell cycle that subsequently leads to inhibition of total RNA and DNA synthesis. Possible mechanisms of this action are discussed. These studies further define the nature of glucocorticoid-induced modulation of human B cell activation and proliferation.     

A tumor cell line producing granulocyte colony-stimulating factor and an immune suppressive factor

From a patient, both a cell line incapable of secreting granulocyte colony-stimulating factor (G-CSF) (TC873) and a cell line capable of secreting G-CSF (TCM902) were established. The effector cells induced, with TC873 cells showed a high lytic capacity against two types of tumor cells. The effector cells induced by TCM902 cells did not show such capacity. Furthermore, the TCM902 cells excreted a factor suppressing the proliferation of lymphokine activated killer (LAK) cells and the autologous tumor cell lysis of tumor associated lymphocytes. This factor probably is TFG- ₁.Abbreviations CSF colony stimulating factor - ELISA enzyme-linked immunosorbent assay - G granulocyte - GM granulocyte-monocyte - IFN interferon - IL interleukin - LAK lymphokine activated killer - M monocyte - MLTC mixed lymphocyte tumor cell culture - TGF transforming growth factor - TILs tumor infiltrating lymphocytes - TNF tumor necrosis factor     

Feedback regulation of immune responses by immune complexes; possible involvement of a suppressive lymphokine by FcR gamma-bearing B cell

Inoculations of antigen-antibody complexes (immune complexes) with the intact Fc portion generates suppressor cells in vivo by binding to FcR gamma on B cells via Fc portions. The cell type responsible for the suppression appears to be B cells bearing FcR gamma. Neither T cells nor macrophages participate in both the inductive and effective phases of this type of regulation. The suppression caused by splenic B cells, previously stimulated with immune complexes in vivo, is mediated by humoral factor(s) released from them. The suppressive factor(s) have H-2 gene product(s) coded by the right-hand side of the H-2 gene complex, but not for FcR gamma themselves or immunoglobulins. It has shared component(s) with suppressive B cell factor (SBF) released from FcR gamma + B cells stimulated with immune complexes in vitro, and it resembles SBF in its mode of action. These findings indicate that immune complexes, the final products of antibody responses, control the immune responses by stimulating surface FcR gamma on B cells. It is of interest that this type of regulation functions in vivo.