Ingeborg Huitinga

West Nile virus neuroinvasion and encephalitis induced by macrophage depletion in mice.

SummaryThe encephalitic West Nile virus and its nonneuroinvasive variant, WN-25, were used to study the effect of macrophage depletion on viral invasion of the central nervous system. The in vivo elimination of macrophages was achieved by use of liposome-encapsulated drug dichloromethylene diphosphonate. Depletion of macrophages had an exacerbating effect on the course of the viral infection, exhibited by higher and extended viremia and accelerated development of encephalitis and death. Using a low dose of West Nile virus (5 PFU/mouse), an increase in mortality (from 50% to 100%) due to macrophage depletion was demonstrated. Furthermore, the attenuated noninvasive variant WN-25 showed high and prolonged viremia in the macrophage depleted mice (≈5 log 10 PFU/ml versus 2 in control mice), that allowed the penetration of the virus into the central nervous system. The mortality rate caused by the attenuated virus in the macrophage-depleted mice was 70–75%, as compared to complete survival in the control inoculated mice. These results indicate a significant role of macrophages in the non-specific immediate defence system of the organism in case of viral infection.

Macrophages in T cell line-mediated, demyelinating, and chronic relapsing experimental autoimmune encephalomyelitis in Lewis rats.

About 50% of the mononuclear cells in the perivascular lesions in the central nervous system (CNS) of rats suffering from experimental allergic encephalomyelitis (EAE) are blood‐borne macrophages. In this study we investigated the role of these macrophages in different variants of EAE, using a liposome‐mediated macrophage depletion technique. Intravenously injected liposomes containing dichloromethylene diphosphonate (C12MDP) are ingested by macrophages and cause temporary and selective elimination of these cells. Macrophage depletion during EAE induced by a T cell line specific for myelin basic protein (MBP; T cell‐EAE) suppresses development of neurological signs of EAE. T cell‐EAE with pronounced demyelination as induced by an additionally injected MoAb directed against myelin oligodendrocyte glycoprotein (MOG) was also significantly ameliorated after macrophage depletion. During chronic relapsing EAE (CR‐EAE) the occurrence of relapses was prevented or suppressed, provided that the liposomes were injected before the initiation of a putative relapse. A chronic progressive course of CR‐EAE was not modified by CI2MDP containing liposome treatment. Histologic examination of the CNS of liposome‐treated animals confirmed decreased infiltration of macrophages into the parenchyma in the rats with T cell and AD‐EAE, whereas T cells were still present.

Selective elimination of macrophages by dichlormethylene diphosphonate-containing liposomes suppresses experimental autoimmune neuritis.

The injection of liposome-encapsulated dichlormethylene diphosphonate (Cl2MDP) constitutes an effective method to selectively eliminate phagocytic cells from spleen, liver and the circulation. We evaluated the effect of Cl2MDP-liposomes on the course of actively induced and adoptively transferred experimental autoimmune neuritis (EAN), both animal models of the human Guillain-Barré syndrome. Injection of Cl2MDP-liposomes 11 and 13 days postimmunization (p.i.) of Lewis rats with bovine peripheral nerve myelin efficiently prevented clinical signs of EAN up to day 15 p.i., when all control animals were affected. Thereafter, EAN gradually also developed in Cl2MDP-liposome-treated rats, but until day 19 disease was significantly milder than in control rats injected with buffer-filled liposomes. Adoptive transfer EAN (AT-EAN) induced by injection of activated P2-specific T cells could be suppressed even more markedly by application of Cl2MDP-liposomes 1, 3, and 6 days after cell transfer. Efficient suppression of AT-EAN by Cl2MDP-liposomes rules out the possibility that EAN is prevented due to interference with the induction phase of this experimental disease and confirms that macrophages are important effector cells during EAN. Selective suppression of phagocytic cell function by drug-containing liposomes may hold promise as a novel treatment of demyelinating autoimmune diseases of the nervous system.

Liposome mediated affection of monocytes.

Dichloromethylene diphosphonate (Cl2MDP) enclosed in liposomes, when injected intravenously, selectively eliminates all phagocytizing macrophages that are in direct contact with the blood circulation of the spleen and the liver. We examined whether Cl2MDP containing liposomes affect, in addition, rat monocytes and bone marrow macrophage precursors (BMMPs). In addition to Phosphatidylcholine-Cholesterol liposomes (PC liposomes), we also used mannosylated PC liposomes (PCMAN liposomes), which are reported to bind more efficiently to macrophages. Monocytes appeared to be affected 24 h after injections of 2 ml of Cl2MDP containing PC as well as PCMAN liposomes. In addition, almost no macrophages could be detected in one week cultures of blood leukocytes isolated from these animals; cultures from control animals contained +/- 50% macrophages. Bone marrow macrophage precursors did not appear to be affected.

The role of macrophage subpopulations in autoimmune disease of the central nervous system

SummaryIn this review the role of various subpopulations of macrophages in the pathogenesis of experimental autoimmune encephalomyetitis is discussed. Immunohistochemistry with macrophage markers shows that in this disease different populations of macrophages (i.e. perivascular cells, microglia and infiltrating blood-borne macrophages) are present in the central nervous system. These subpopulations partially overlap in some functional activity while other activities seem to be restricted to a distinct subpopulation, indicating that these subpopulations have different roles in the pathogenesis of encephalomyelitis. The studies discussed in this review reveal that immunocytochemical and morphological studies, combined with new techniques such asin situ nick translation and experimental approaches like the use of bone marrow chimeras and macrophage depletion techniques, give valuable information about the types and functions of cells involved in central nervous system inflammation. The review is divided in three parts. In the first part the experimental autoimmune encephalomyelitis model is introduced. The second part gives an overview of the origin, morphology and functions of the various subpopulations. In the third part the role of these subpopulations is discussed in relation to the various stages (i.e. preclinical, clinical and recovery) of the experimental disease.

Expression of the ED3 Antigen on Rat Macrophages in Relation to Experimental Autoimmune Diseases

Susceptibility to experimental autoimmune diseases (EAD) is rat strain dependent. Susceptible animals are reported to have a defective glucocorticoid response. Although many EAD are regarded as preferentially T cell-mediated, macrophages (M phi) play an important role in several different stages of these diseases. In this study we have investigated the possible effect of the disturbed hypothalamic-pituitary (HPA) axis on M phi phenotype. Therefore we studied M phi differentiation in several different rat strains, especially with regard to the M phi specific differentiation antigen as recognized by monoclonal antibody (mAb) ED3. This mAb is, in normal healthy rats, reactive with very restricted M phi subpopulations present in the lymphoid organs only. However, in autoimmune diseased tissues many of the infiltrated M phi are also ED3-positive. It appeared that M phi, in vitro derived from monocytes out of susceptible rat strains, showed a high ED3 expression in contrast to monocyte-derived M phi out of resistant rat strains. This difference in ED3 expression appeared to be T cell-mediated. Our results are suggestive for the fact that the impaired HPA-axis in EAD susceptible rat strains affects M phi differentiation. The relevance of the observed differences with respect to disease induction, maintenance, or suppression is discussed and obviously needs further investigation.

Demonstration of adhesion molecules on macrophages and glial cells during acute and chronical experimental allergic encephalomyelitis

Neuroimmune Interactions and their Regulation A satellite conference of the International Congress of Immunology Budapest, Hungary, 1992 August 20-22 The following abstracts are from the neuroimmunology meeting that was presented as a satellite meeting to the 8th International Congress of Immunology held in Budapest, Hungary, this summer. The selection of this topic by the International Organizing Committee recognizes the rapid development of neuroimmunology as a discipline which bridges the gap between immunology and neuroscience. Experimental and clinical researchers were present and gave an extensive overview of some of the most promising areas of basic research in neuroimmunology today. The presentations focused on the molecular mechanisms of cell-cell interactions between the immune system and cells of the central nervous system, leukocyte migration into the central nervous system, the role of T cell receptors in diseases of the central nervous system, and the interactions between the neuroendocrine and immune systems (mediators and receptors). The active participation in the discussion of these new areas in neuroimmunology was extensive and very gratifying to the organizers of the satellite meeting: Drs. Zsuzsanna Fabry and Michael N. Hart of the University of Iowa Department of Pathology (Neuropathology) and Dr. Cedric Raine of the Department of Neuropathology at Albert Einstein College of Medicine. The success of the satellite meeting was enhanced by having the posters and poster workshops in the same room which created an atmosphere highly conducive to the informal exchange of ideas, while the pleasant social environment provided an excellent setting for late night discussion outside the lecture halls. Immunosuppression by delta opioid receptor antagonist (naltrindole, NTI) K. Arakawa a, T. Akami a, M. Okamoto a, T. Oka a and H. Nagase b a Second Department of Surgery, Kyoto Prefectural University of Medicine, Kawaramachi, Kamikyo, Kyoto, Japan, and b Basic Research Laboratories, Toray Industries, Inc., Tebiro, Kamakura, Kanagawa, Japan Recently, a delta receptor antagonist (naltrindole, NTI) has been shown to inhibit the activities of B cells and natural killer (NK) cells. In this study, we have investigated the immunosuppressive effect of NTI on rat kidney allograft survival. LEW recipients of Baffalo rats (BN) kidney allografts were treated with NTI subcutaneously for 7 postoperative days. Non-treated kidney allografts were rejected within 16 days (n = 10, median survival time (MST)= 9.3 + 3.0 days). NTI treatment significantly prolonged allograft survival at a dose of 0.2 mg kg-1 day-1 (MST = 46.5 _+ 25.3 days, P < 0.01) and 2.0 mg kg -1 day -1 (MST= 78.1 + 34.7 days, P < 0.01). To study the immunosuppressive effect of NTI in the genetically stronger allograft combination in which MST = 7.3 + 1.0 days (n = 9), BN kidneys were transplanted to LEW recipients. NTI prolonged the kidney allograft survival at a dose of 2.0 mg kg-1 day-1 (MST = 12.9 + 10.7 days, P < 0.05). More remarkable prolongation of allograft survival was observed at a higher dose of NTI, 10.0 mg kg -1 day-1 (MST = 37.6 + 43.1 days, P < 0.01). The dose of NTI used (0.2-10.0 mg kg -1 day -1) was not toxic in vivo. Thus, delta opioid receptor antagonist, NTI, is a newly developed, safe and useful immunosuppressive agent for organ transplantation. Demonstration of adhesion molecules on macrophages and glial cells during acute and chronical experimental allergic encephalomyelitis J. Bauer, C.D. Dijkstra, I. Huitinga and T. Sminia Department of Cell Biology, Vrije Universiteit, Amsterdam, Netherlands Several reports have described the expression of adhesion molecules on endothelial cells in the central

Macrophages: Effectorcells in experimental allergic encephalomyelitis

ENCEPHALOMYELITIS (EAE) ITS POSSIBLE IMPLICATIONS M.P. Pender .~, K.B. Nguyen 1, P.A. MeCombe 1, and J.F.R. Kerr 2 tDepartment of Medicine and 2Department of Pathology, University of Queensland, Brisbane, Australia. Apoptos|s ~s an active process of cellular self-destruction that often serves a biologically meaningful homeostatic function. Here we report apoptosis in the spinal cord in 4 forms of EAE in the Lewis rat: (l) acute EAE induced by inoculation with whole spinal cord; (2) acute EAE induced by inoculation with myelin basic protein (MBP); (3) acute EAE passively transferred by MBP-sensitized splenocytes; (4) chronic relapsing EAE. Cells undergoing apoptosis were recognized at light and electron microscopy by the presence of either crescentic masses of condensed chromatin lying against the nuclear envelope or rounded masses of uniformly dense ehromatin. Although it was not possible to identify definitively the types of cells undergoing apoptosis, the size and location of some of the affected cells suggested that they were o!igodendrocytes. As there is now much evidence that T-cell-induced target cell death takes the form of apoptosis, it is attractive to hypothesize that oligodendrocyte apoptosis is occurring in EAE as a result of oligodendrocyte-directed T-cell eytotoxicity. However, other apoptotie cells were located within the myelin sheath, meninges and perivaseular spaces and were clearly not oligodendroeytes but were most likely blood-derived mononuelear cells. The sparsity of their cytoplasm and the absence of phagocytosed material suggested that they were mainly lymphoeytes rather than macrophages. Apoptosis has been shown to be involved in deleting autoreaetive T-cells in the thymus during the normal development of tolerance. Thus apoptotie deletion of myelin/oligodendrocyte-specifie T-cells in the central nervous system in EAE might explain both the subsidence of inflammation and the acquisition of tolerance in this autoimmune disease. As apoptosis is an active process that can be controlled, agents that modulate its occurrence may prove useful in the therapy of inflamma:ory demyelinating disease.