Gamma interferon, CD8+ T cells and antibodies required for immunity to malaria sporozoites

This study was designed to test the hypothesis that T-cell effector mechanisms are required for protective immunity to malaria sporozoites. Administration of neutralizing monoclonal antibodies against gamma interferon (gamma IFN) to immune hosts, reversed sterile immunity to sporozoite challenge, by allowing the growth of exoerythrocytic forms (EEF) and thus the development of parasitaemia. Immune animals also developed infections when depleted in vivo of their suppressor/cytotoxic T cells expressing the CD8 antigen (CD8+) but not when depleted of helper T cells expressing CD4 antigen (CD4+), before sporozoite challenge. Passive transfer of immune immunoglobin alone, or adoptive transfer of immune T cells alone, conferred partial protection to naive recipients. Transfer of both immune components resulted in significantly greater protection. This transferred immunity was reversed by the in vivo neutralization of gamma IFN. Thus, sterile immunity to sporozoite challenge requires the neutralization of sporozoites by antibodies and the inhibition of EEF development by gamma IFN with the participation of CD8+ cells.     

Cyclosporine induces cancer progression by a cell-autonomous mechanism

Malignancy is a common and dreaded complication following organ transplantation. The high incidence of neoplasm and its aggressive progression, which are associated with immunosuppressive therapy, are thought to be due to the resulting impairment of the organ recipient's immune-surveillance system. Here we report a mechanism for the heightened malignancy that is independent of host immunity. We show that cyclosporine (cyclosporin A), an immunosuppressant that has had a major impact on improving patient outcome following organ transplantation, induces phenotypic changes, including invasiveness of non-transformed cells, by a cell-autonomous mechanism. Our studies show that cyclosporine treatment of adenocarcinoma cells results in striking morphological alterations, including membrane ruffling and numerous pseudopodial protrusions, increased cell motility, and anchorage-independent (invasive) growth. These changes are prevented by treatment with monoclonal antibodies directed at transforming growth factor-beta (TGF-beta). In vivo, cyclosporine enhances tumour growth in immunodeficient SCID-beige mice; anti-TGF-beta monoclonal antibodies but not control antibodies prevent the cyclosporine-induced increase in the number of metastases. Our findings suggest that immunosuppressants like cyclosporine can promote cancer progression by a direct cellular effect that is independent of its effect on the host's immune cells, and that cyclosporine-induced TGF-beta production is involved in this.     

The synthesis and in vivo assembly of functional antibodies in yeast

The yeast Saccharomyces cerevisiae can synthesize, process and secrete higher eukaryotic proteins. We have investigated the expression of immunoglobulin chains in yeast and demonstrate here the synthesis, processing and secretion of light and heavy chains, the glycosylation of heavy chain, the intracellular localization of these foreign proteins by immunofluorescence, and the detection of functional antibodies in cells co-expressing both chains. This may provide the basis of a microbial fermentation process for the production of monoclonal antibodies. The co-expression of light and heavy chains in Escherichia coli has been reported but functional antibodies were not assembled in vivo. Furthermore, only low-level assembly of these chains was found in vitro.     

Suppression of experimentally induced autoimmune encephalomyelitis by cytolytic T-T cell interactions

Down-regulatory phenomena have been described in several experimental models of tissue-specific, T-cell-mediated autoimmunity. For example, resistance to active induction of experimental autoimmune encephalomyelitis (EAE) can be induced by pretreating animals with non-pathogenic inocula of autoantigen or effector cells. Moreover, animals that have recovered from one EAE episode are resistant to subsequent induction of EAE. In some models, resistance to EAE has been transferred with immune cells to naive recipients. These experiments, which were based on transfers of unseparated immune cell populations, are difficult to interpret. Immune suppression circuits are known to be complex and involve various distinct cellular subsets. To further complicate the issue, resistance to EAE can be transferred not only by suppressor cells, but also by encephalitogenic effector cells injected in 'subclinical' doses. We describe now the isolation of homogeneous T lymphocyte lines from the spleens of Lewis rats that had recovered from T-cell-mediated EAE (tEAE) caused by the MBP-specific T cell line S1. These spleen-derived T line cells express the CD8 phenotype and specifically respond to determinants on the inducing S1 line, but not to the autoantigen MBP. Furthermore, the anti-S1 cells selectively lyse the encephalitogenic S1 T line in vitro and efficiently neutralize their encephalitogenic capacity in vivo.     

Regulatory properties of LFA-1 alpha and beta chains in human T-lymphocyte activation

Lymphocyte function-associated antigen-1 (LFA-1) is a heterodimer composed of an alpha and beta chain that is expressed on the surface of most leukocytes and is an essential molecule for adhesion reactions between cells participating in the immune response. A putative ligand for LFA-1 is the intercellular adhesion molecule ICAM-1 (refs 3-5). Leukocyte adhesion abnormality is found in patients with LFA-1 deficiency. It is not clear whether binding of ligand to the LFA-1 molecule merely spatially orientates cells towards each other or can also induce signals that regulate cell activation and differentiation. We have recently developed a T-cell proliferation assay which uses immobilized anti-CD3 monoclonal antibodies as stimulant and is independent of LFA-1-mediated cellular adhesion. As there is no interference by anti-LFA-1 monoclonal antibodies with the adhesion-dependent activation steps, this T-cell activation system allows us to investigate whether transmembrane signals are induced by binding of ligand to LFA-1 on T cells. Our data indicate that binding of ligand to LFA-1 results in the transduction of regulatory signal across the plasma membrane, rather like other molecules (CD2, CD4, CD8) (refs 8-11) with signal-modifying properties involved in the adhesion of T cells to target/stimulator cells. Indeed, adhesion molecules might generally be important in signal transduction, even in cells not belonging to the immune system.     

Immunization to a syngeneic sarcoma by a monoclonal auto-anti-idiotypic antibody

Idiotypic networks regulate the immune response to a variety of antigens. Antibodies generated against other antibodies, called anti-idiotypic antibodies, can themselves mimic antigen and elicit a specific immune response. They have been shown to induce delayed-type hypersensitivity (DTH) to model antigens in the mouse. As anti-idiotypic antibodies are thought to be involved in the response to tumour-associated antigens we tested whether injection of monoclonal antibodies derived from mice hyperimmunized to a syngeneic, chemically induced sarcoma could mimic antigen and induce DTH to the sarcoma in naive mice. One of the monoclonal antibodies, 4.72, primed BALB/c mice for DTH to the sarcoma but not for DTH to another sarcoma or to sheep erythrocytes. Antibody 4.72 did not induce DTH in mice of immunoglobulin allotype congeneic strains nor did it bind to the sarcoma cells. As antibodies specific for this sarcoma have not been detected, we do not know whether idiotype on immunoglobulin molecules is recognized by antibody 4.72. However, as the response induced by antibody 4.72 was both antigen-specific and allotype-restricted, analogous to those induced by anti-idiotypic antibodies in other systems, we propose that antibody 4.72 is an anti-idiotypic antibody.     

Detection of P-glycoprotein in multidrug-resistant cell lines by monoclonal antibodies

One reason for the failure of chemotherapy in the treatment of advanced cancers may be the outgrowth of multidrug-resistant tumour cells. Multidrug resistance has been modelled in numerous mammalian cell lines in which the phenotype is characterized by a pleiotropic cross-resistance to unrelated drugs. In the study reported here, we have produced monoclonal antibodies whose binding to plasma membranes of different multidrug-resistant mammalian cells correlates with the degree of drug resistance. All these antibodies are specific for P-glycoprotein, a cell surface component of relative molecular mass (Mr) 170,000 (170K) that has been described previously, and are directed against three spatially distinct epitopes which define a conserved cytoplasmic domain in the C-terminal region of the P-glycoprotein polypeptide. The conserved nature of P-glycoprotein and its low-level expression is drug-sensitive cells suggest that it has an important function at the cell surface. The monoclonal antibodies against P-glycoprotein described here might serve as diagnostic reagents for clinically unresponsive tumours.     

ICAM-1 a ligand for LFA-1-dependent adhesion of B, T and myeloid cells

Cell-cell adhesion is essential for many immunological functions. The LFA-1 molecule, a member of a superfamily of adhesion molecules, participates in adhesion which is critical to the function of each of the three major subsets of leukocytes: lymphocytes, monocytes and granulocytes. Putative LFA-1 ligands have been identified functionally in different laboratories using three different monoclonal antibodies that inhibit LFA-1-mediated leukocyte adhesion in particular model systems; however, there may be more than one LFA-1 ligand. We have directly compared the three relevant monoclonal antibodies, and show that each binds to the same molecule, intercellular-adhesion molecule-1 (ICAM-1). Most important, B, T and myeloid cells adhere specifically to purified ICAM-1-coated surfaces; such adhesion has distinctive requirements for Mg2+ and Ca2+. This constitutes biochemical evidence that ICAM-1 functions as a ligand for LFA-1-dependent adhesion by a variety of leukocytes.     

Expression of interleukin-2 receptors as a differentiation marker on intrathymic stem cells

The thymus is regarded as the primary site for T-cell lymphopoiesis, but very little is known about the lineage inter-relationships of cells within that organ. At least four subpopulations of mouse thymocytes can be defined on the basis of staining with monoclonal antibodies directed against the T-cell differentiation antigens Lyt-2 and L3T4 (ref. 2). Thus immunocompetent (medullary) thymocytes, like peripheral T cells, express either Lyt-2 (cytotoxic phenotype) or L3T4 (helper phenotype) but not both, whereas non-functional (cortical) thymocytes express both markers. In addition, a small subpopulation comprising 2-3% of cells in the thymus and expressing neither Lyt-2 nor L3T4 has recently been described. The latter cells have the properties of intrathymic 'stem cells' in that they are the first to appear in the embryonic thymus and at least some can be shown to give rise, both in vivo (ref. 4. and our unpublished data) and in vitro, to other thymocyte subpopulations. We show here that 50% of Lyt-2-/L3T4- cells in the adult thymus express receptors for the polypeptide growth hormone interleukin-2 (IL-2) whereas other cells in the thymus do not. Furthermore, immunohistochemical localization studies on frozen sections indicate a disperse distribution of IL-2 receptor-positive cells in both the cortex and medulla. These novel findings have potential implications in the context of current models of differentiation pathways within the thymus.     

褪黑素单克隆抗体的制备及鉴定

为了获得抗褪黑素(MT)高效价的单克隆抗体,用甲醛将MT连结到BSA上,然后用连结物背部皮下多点免疫Balb／c小鼠,用PEG诱导免疫鼠脾细胞与Sp2／0细胞融合,经ELISA法筛选阳性克隆株及测定效价,用抗体与同类物之间的交叉反应进行特异性鉴定．最后获得5株(4C9D7、3E12C7H11E7、3E12A9D7、6A6A3A2C3、1E1E2H2H6)能稳定分泌高效价抗MT的单克隆抗体(McAb)的杂交瘤细胞。     

Thy-1-mediated T-cell activation requires co-expression of CD3/Ti complex

In addition to monoclonal antibodies against the CD3 (T3)-T-cell antigen receptor (CD3/Ti) complex, several other monoclonals directed towards distinct cell surface structures on human (CD2 (T11) and Tp44) and murine (Thy-1, TAP, and Ly-6) T lymphocytes are capable of activating T cells. It has been proposed that such structures may function as alternative pathways of stimulation. To examine directly whether any relationship exists between Thy-1-dependent activation phenomena and T-cell activation mediated through the CD3/Ti complex, we have transfected several CD3/Ti- variants of the human T-cell line Jurkat with the murine Thy-1.2 gene. Our data indicate that in CD3/Ti-, Thy-1.2+ transfectants, monoclonal antibodies against Thy-1.2 can induce a rise in cytoplasmic free calcium ([Ca2+]i), but fail to stimulate interleukin-2 (IL-2) production. The only defect in these variant cell lines responsible for the inability to produce IL-2 in response to Thy-1 stimulation was in the expression of the CD3/Ti complex, because replacement of defective Ti alpha- or beta-chain genes reconstributed both surface expression of CD3/Ti and responsiveness to Thy-1 in the IL-2 production assay.     

Class IV semaphorin Sema4A enhances T-cell activation and interacts with Tim-2

Semaphorins are a family of phylogenetically conserved soluble and transmembrane proteins. Although many soluble semaphorins deliver guidance cues to migrating axons during neuronal development, some members are involved in immune responses. For example, CD100 (also known as Sema4D), a class IV transmembrane semaphorin, signals through CD72 to effect nonredundant roles in immune responses in a ligand-receptor system that is distinct from any seen previously in the nervous system. Here we report that the class IV semaphorin Sema4A, which is expressed in dendritic cells and B cells, enhances the in vitro activation and differentiation of T cells and the in vivo generation of antigen-specific T cells. Treating mice with monoclonal antibodies against Sema4A blocks the development of an experimental autoimmune encephalomyelitis that is induced by an antigenic peptide derived from myelin oligodendrocyte glycoprotein. In addition, expression cloning shows that the Sema4A receptor is Tim-2, a member of the family of T-cell immunoglobulin domain and mucin domain (Tim) proteins that is expressed on activated T cells.     

Construction of chimaeric processed immunoglobulin genes containing mouse variable and human constant region sequences

The specificity of monoclonal antibodies provides a powerful diagnostic and therapeutic tool in investigating human neoplasia. Radiological scanning and immunotherapy with mouse tumour-specific monoclonal antibodies have been applied to patients with some success, but a major problem is the neutralization of the mouse antibody induced by repeated administration of heterologous antibodies. To avoid or reduce such immune reactions, chimaeric immunoglobulins consisting of mouse variable (V) and human constant (C) regions can be synthesized. We have constructed a recombinant retrovirus DNA carrying genomic heavy-chain (H) variable-diversity joining (VH-D-JH) and C gamma 1 genes from different species and show here that the chimaeric intervening sequences are spliced out precisely. This procedure provides a useful method to construct the chimaeric mouse-human immunoglobulin gene to be expressed in Escherichia coli, yeast and animal cells. Unexpectedly, a hidden splice donor site in the 5'-flanking region of a human VH gene is used in place of the donor site of the leader sequence exon, resulting in the formation of the V region without the leader sequence.     

PD-1/PD-L1抗体阻断药物的研究进展与临床应用

研究发现在生理状况下PD-1与PD-L1相互识别能产生负向信号,该信号通路一旦被激活后,可诱导抗原特异性效应T细胞凋亡,该生理效应可防止过度免疫反应带来的附加损伤,因此该信号通路又被形象的称为“免疫刹车”.如果利用特异性阻断剂阻断PD-1/PD-L1信号通路,便可以恢复免疫细胞的杀伤抑制功能.截止至2019年12月,全...     

Monoclonal antibodies which recognize different cell types in the rat retina

Seven monoclonal antibodies have been produced against a membrane preparation from adult rat retina. Three antibodies reacted with particular regions of rat photoreceptor cell surfaces: RET-P1 labelled the cell bodies, outer and inner segments (rods but not cones), RET-P2 labelled only outer segments and RET-P3 labelled only the cell bodies. Three antibodies reacted with glial cells; RET-G2 and RET-G3 were specific for Müller cells, RET-G1 also labelled glia elsewhere in brain. The seventh antibody (RET-N1) reacted with many types of neuronal cells.     

Molecular identification of a danger signal that alerts the immune system to dying cells

In infections, microbial components provide signals that alert the immune system to danger and promote the generation of immunity. In the absence of such signals, there is often no immune response or tolerance may develop. This has led to the concept that the immune system responds only to antigens perceived to be associated with a dangerous situation such as infection. Danger signals are thought to act by stimulating dendritic cells to mature so that they can present foreign antigens and stimulate T lymphocytes. Dying mammalian cells have also been found to release danger signals of unknown identity. Here we show that uric acid is a principal endogenous danger signal released from injured cells. Uric acid stimulates dendritic cell maturation and, when co-injected with antigen in vivo, significantly enhances the generation of responses from CD8+ T cells. Eliminating uric acid in vivo inhibits the immune response to antigens associated with injured cells, but not to antigens presented by activated dendritic cells. Our findings provide a molecular link between cell injury and immunity and have important implications for vaccines, autoimmunity and inflammation.     

Rejection of transplantable AKR leukaemia cells following MHC DNA-mediated cell transformation

Major histocompatibility complex (MHC) class I molecules can function as specific target antigens in T-cell-mediated cytotoxity. In addition, T cells can kill target cells through non-MHC antigens, for example, virally infected cells, if the target and effector cells express the same MHC class I antigens. Consequently, quantitative and/or qualitative variations in the expression of the H-2/HLA antigens on the target cells could interfere with MHC-restricted immune reactions. We have reported that the AKR leukaemia cell line K36.16, a subline of K36 (ref. 3), on which the H-2Kk antigen cannot be detected, is resistant to T-cell lysis and grows very easily in AKR mice. Other AKR tumour cell lines, like 369, which have a relatively large amount of H-2Kk on their surface, are easily killed by T cells in vitro and require a much larger inoculum to grow in vivo. Monoclonal antibodies against H-2Kk, but not against H-2Dk, prevented the killing by T cells. This suggests that some tumour cells grow in vivo because tumour-associated antigen(s) cannot be recognized efficiently by the host's immune system, due to the absence of MHC molecules which would function as restriction elements for T-cell cytotoxicity. We have tested this hypothesis by introducing the H-2Kk gene into the H-2Kk-deficient AKR tumour cell line K36.16 and have now demonstrated directly the biological relevance of H-2Kk antigen expression in the regulation of the in vivo growth of this tumour cell line.     

A new immunomodulating compound (AS-101) with potential therapeutic application

There has been interest in the potential of synthetic compounds to modify immune responses by imitation of cytokine action. Direct administration of interleukin 2 (IL-2) in conjunction with adoptive transfer of lymphokine activated killer cells has been used in the treatment of cancer, but there are toxic effects resulting from the high doses of IL-2 required. We have developed a new synthetic compound, ammonium tri-chloro(dioxoethylene-O,O'-)tellurate (AS-101), which has immunomodulating properties and minimal toxicity. The effects of AS-101 on the activation and function of immunocompetent cells have been assessed. We have found that AS-101 induces proliferation and IL-2 production by human lymphocytes in vitro, and enhances the production of IL-2 and colony-stimulating factor by mouse spleen cells. Splenocytes of BALB/c mice injected with AS-101 increased production of IL-2 and CSF in vitro in the presence of mitogen. Mononuclear cells of normal donors acquired responsiveness to recombinant IL-2 and bound monoclonal antibody to IL-2 receptor after incubation with AS-101. Splenocytes of mice treated in vivo with AS-101 expressed high levels of IL-2 receptor. The stimulation of lymphocytes by AS-101 apparently involves an increase in intracellular free calcium. AS-101 administered systemically to mice mediated antitumour effects which could be attributable to its immunomodulatory properties. In addition, AS-101 could directly enhance the ratio of OKT4 to OKT8-positive cells in cultured mononuclear cells from AIDS (acquired immune deficiency syndrome) patients. These results indicate that AS-101 is potentially useful in the treatment of clinical conditions involving immunosuppression.     

Anti-HLA-A2 antibody-enhancement of peptide association with HLA-A2 as detected by cytotoxic T lymphocytes

Most cytotoxic T lymphocytes (CTL) not only recognize epitopes of viral or other foreign proteins in association with class I major histocompatibility complex (MHC) molecules, but also recognize target cells sensitized with short synthetic peptides representing the epitopes. There is increasing evidence that these synthetic peptides associate with the class I molecule both at the cell surface and intracellularly. We have now investigated the effect of a monoclonal antibody specific for HLA-A2 and HLA-B17 (B57/58) molecules (antibody MA2.1)3 on the sensitization of target cells with peptide for lysis by HLA-A2-restricted CTL. Previously, anti-HLA class I monoclonal antibodies have been shown to inhibit the recognition of target cells, infected with influenza A virus, by virus-specific CTL. We find, however, that target cells treated with MA2.1 antibody can be sensitized with peptide for CTL lysis much more rapidly than untreated cells, or at greater than 100-fold lower peptide concentration than that required for sensitization of untreated cells. This implies that the antibody, which is believed to bind to one side of the peptide-binding groove, directly affects the binding of peptide to the HLA-A2 molecule at the cell surface.