Amelioration of intrathymic T cell development and peripheral T cell reactivities in autoimmune mice undergoing therapy with a novel immunomodulator

MRL lpr/lpr mice develop a generalized autoimmune disease associated with a massive accumulation in the peripheral lymphoid organs of abnormal, phenotypically immature T cells. Both the lymphoadenopathy and the autoimmunity are thymus-dependent and likely to arise from an aberrant pathway of intrathymic differentiation. We here present the marked beneficial effects acquired in MRL lpr/lpr mice after in vivo administration of a novel immunomodulator called linomide. The highly altered pattern of thymic subpopulations in MRL lpr/lpr mice is normalized after linomide-treatment. Concomitantly, the peripheral T cell compartment, which in MRL lpr/lpr is highly deficient in producing and responding to IL-2, gains substantial functional reactivities. We propose that linomide acts by correcting the abnormal T cell development in autoimmune MRL lpr/lpr mice. This new immunomodulator may be a useful tool for providing insight into both the pathogenesis of autoimmune disorders and intrathymic differentiation.     

Immunomodulatory effects of linomide in animals immunized with immunopathogenic retinal antigens: dissociation between different immune functions

Linomide (LS-2616, quinoline-3-carboxamide) has been reported to exert a diverse range of effects on the immune system. On one hand, this drug was found to stimulate the immune system and to enhance activities such as DTH or allograft rejection. On the other hand, linomide was shown to inhibit the induction of experimental autoimmune encephalomyelitis and myasthenia gravis, as well as the development of diabetes in non-obese diabetic (NOD) mice. Here we report the effects of linomide in animals immunized with uveitogenic retinal antigens. Treatment with linomide completely inhibited the development of experimental autoimmune uveoretinitis (EAU) in mice immunized with interphotoreceptor retinoid-binding protein and markedly suppressed EAU in rats immunized with S-antigen (S-Ag). In addition, linomide-treated rats exhibited reduced antibody production and lymphocyte proliferative response to S-Ag. In contrast to these suppressive activities, linomide treatment did not affect the development of adoptively transferred EAU in rats and moderately enhanced the DTH reactions to S-Ag in immunized rats in which EAU and other immune responses to this antigen were suppressed.     

Linomide, an immunomodulator that inhibits Th1 cytokine gene expression

Linomide (LS-2616, quinoline-3-carboxamide) has strong immunomodulatingeffects in animal models, inhibiting toxic shock, progressiveautoimmune disease and cancer. In humans, linomide stronglyreduced the appearance of new lesions in multiple sclerosisyet enhanced immune responses after bone marrow transplantation.In contrast to these clear effects in vivo, attempts to showan effect of linomide in vitro have not been successful andits mode of action remains to be elucidated. Here we show thatat concentrations effective in vivo, linomide is active on humanperipheral blood mononuclear cells (PBMC), severely inhibitingthe induction by Staphylococcus aureus enterotoxin B of mRNAof three cytokine genes expressed in T_h1 cells, those for IFN-,IL-2, and tumor necrosis factor-ß. Yet, cell viabilitywas not affected by linomide. The extent of inhibition is dose-dependenton linomide. Linomide also blocked induction of IL-2 and IFN-mRNA by phytohemagglutinin. The inhibitory effect is expressedimmediately but can be enhanced significantly by a prolongedexposure of PBMC to linomide, reaching 10-fold. These resultssupport the concept that linomide antagonizes the activationof T_h1 cells during a cellular immune response.     

Multiformic modulation of endotoxin effects by linomide

Linomide is a potent immunomodulator that either enhances or suppresses certain immunological processes. Of particular interest is this compound's capacity to inhibit a variety of organ-specific autoimmune diseases. Here, we report on the effects of linomide on several immunological reactions elicited by endotoxin (LPS), both in vivo and in vitro. In rats and mice linomide inhibited the elicitation of endotoxin-induced uveitis (EIU), an acute inflammatory eye disease that develops within 24 h following footpad injection of LPS. Linomide also inhibited the production of TNF-alpha and IL-6 by LPS-stimulated rat and mouse macrophage monolayers. On the other hand, treatment with linomide significantly increased the levels of IL-1beta (mice and less in rats), IL-6 (rats), and TNF-alpha (mice) in serum samples collected 2 h following injection with LPS. The increased production of proinflammatory cytokines in linomide-treated mice was also indicated by the enhanced lethal effect of LPS in these mice. The finding of elevated levels of these cytokines in animals with suppressed EIU is also in line with previous observations of an inverse relationship between EIU severity and levels of TNF-alpha. Data recorded here underscore the unique capacity of linomide to both enhance and suppress the immune system.     

The antiangiogenic agent linomide inhibits tumor necrosis factor-α secretion via inhibition of its synthesis

We have previously reported that linomide, a quinoline-3-carboxamide, has antitumor effects against prostatic cancers in vivo through its ability to inhibit tumor angiogenesis. Subsequently, we reported that linomide inhibits several steps in the process of angiogenesis, including direct effects on endothelial cell proliferation and their chemotactic migration and invasion. Besides these direct effects, linomide's antiangiogenic activity also involves indirect effects secondary to inhibition of tumor infiltration of macrophages and their ability to secrete the angiogenic factor tumor necrosis factor-α (TNF-α). The current studies were conducted to gain insight into the mechanism by which linomide inhibits macrophage TNF-α secretion. The virally transformed RAW 264.7 mouse macrophage cell line was used as a model system. Chronic in vitro exposure (7 days) to 81-650 μM linomide is cytostatic to RAW cells. Such chronic exposure to linomide significantly decreased (P < 0.05) RAW cells' baseline ability to secrete TNF-α and also their ability to up-regulate TNF-α secretion in response to lipopolysaccharide (LPS) challenge. Ribonuclease protection assays demonstrated that linomide's ability to inhibit baseline and LPS-challenged TNF-α secretion is not functioning at the mRNA level, because steady-state levels of TNF-α mRNA do not change in response to linomide. Linomide's ability to inhibit TNF-α secretion is not associated with an increase in cell-associated TNF-α levels. Immunoprecipitation experiments demonstrated that linomide did not inhibit the normal proteolytic processing of the initial 26 kDa plasma membrane-bound TNF-α to the secreted 17 kDa soluble form. These results demonstrate that linomide inhibits TNF-α secretion by inhibition of the synthesis of the TNF-α protein. Linomide's ability to inhibit TNF-α protein synthesis is not due to an inhibition of general protein synthesis or secretion and is not mediated via a change in cyclic adenosine monophosphate levels. © 1996 Wiley-Liss, Inc.     

Treatment of Minimal Residual Diseasein Myeloid Leukemia—The Immunotherapeutic Options with Emphasis on Linomide

It is now known that syngeneic transplantation, T lymphocyte depletion and absence of graft-versus-host disease all increase the risk of relapse following allogeneic transplantation for the myeloid leukemias, both acute and chronic. Leukemia-specific immune responses appear to play a major role in the therapy of the myeloid leukemias. In recent years attempts have been made to better characterize and effectively utilize these antileukemic immune responses, concentrating on clinical states of minimal residual disease. This review will discuss the role of such immunotherapy following autologous bone marrow transplantation for myeloid leukemias, and will focus on recent experience and ongoing clinical trials using the novel immunomodulator Linomide.