Effect Of Macrophage Depletion Research Articles

Effect of macrophage depletion by liposomes containing dichloromethylene-diphosphonate on endotoxin-induced uveitis

Footpad injection of lipopolysaccharide (LPS) from Salmonella typhimurium in Lewis rats induces an acute anterior and posterior endotoxin-induced uveitis (EIU). To investigate the role of macrophages in the pathogenesis of EIU, we eliminated macrophages by means of liposomes containing dichloromethylene-diphosphonate (Cl 2MDP), a drug which depletes macrophages but not other immunocompetent cells. Intravenous injection of CL 2MDP-liposomes clearly inhibited clinical and histological manifestations of uveitis in the anterior segment of the eye (iris/ciliary body) and reduced TNF level in aqueous humor. Specific immunostaining showed that CL 2MDP-liposome injections decreased the number of ED2+ resident macrophages in the iris/ciliary body and the choroid. After LPS injection, CL 2MDP-liposome treatment reduced the density of infiltrating ED1+ cells (mainly monocytes/macrophages) in the iris/ciliary body but not in the choroid; little or no effect was detected on the OX42+ cellular infiltration (mainly polymorphonuclear leukocytes). The inflammatory cellular infiltration of the retina was not modified by the treatment. These findings suggest that macrophages play a key role in the pathogenesis of ocular inflammation.

Effects of macrophage depletion and anti-CD40 ligand on transgene expression and redosing with recombinant adenovirus.

The anti-CD40 ligand antibody MR-1, and macrophage-depleting liposomes were tested for their ability as transient immunosuppressive agents to: (1) prolong transgene expression; and (2) permit redosing after recombinant adenovirus infusion of mice. To test for effect on transgene duration, mice were infused with recombinant adenovirus coding for human factor IX (AdFIX), and plasma FIX levels monitored over time. Treatment with either agent significantly prolonged transgene expression. Persistence was accompanied by inhibition of anti-adenovirus (anti-Ad) IgG, and decreased IL-10 and IFN-gamma production from splenic lymphocytes re-exposed to virus particles in vitro. To test for effect on redosing, mice were given a primary infusion of recombinant adenovirus coding for bacterial beta-galactosidase (Ad beta gal), followed by secondary and tertiary infusions of AdFIX on days 24 and 63. Mice that had received MR-1 had low to undetectable anti-Ad on day 24, and efficient transduction occurred. Furthermore, FIX levels endured in these mice, with 40% retention of FIX on day 63, in contrast to rapid loss in naive controls. On day 63, the continuance of negligible anti-Ad levels correlated with successful tertiary transduction. These results suggest that both macrophage depletion and CD40 ligand blockade inhibit immune responses to recombinant adenovirus to slow decline of transgene expression, while only CD40 ligand blockade inhibits anti-Ad antibody generation sufficiently to allow redosing to the liver.

Marrow-derived activated macrophages are required during the effector phase of experimental autoimmune uveoretinitis in rats

Purpose. Experimental autoimmune uveoretinitis (EAU), an established model for human endogenous (autoimmune) posterior uveitis, is a CD4+ T cell-mediated disease inducible in Lewis rats by intradermal inoculation with retinal antigens. Immunohistochemical studies have previously documented the lymphocyte profiles during various stages of the disease process. The purpose of the present study was to investigate the role of macrophages in EAU.Methods. EAU was induced in Lewis rats, and the effect of macrophage depletion, using the drug dichlorodimethylene diphosphonate (Cl2MDP) encapsulated in liposomes and administered intravenously, was assessed based on the clinical and histological profile of the disease.Results. The results have shown that in control animals macrophages occur early, feature prominently throughout the course of the disease and display considerable heterogeneity: marrowderived ED1+ cells and ED3+ cells are the major infiltrating cells, with many cells also expressing ED7 and ED8. In contrast, few cells expressed the ED2 antigen during EAU, even though ED2+ “resident” macrophages occur in the normal choroid. Macrophage depletion, using intravenously injected dichloromethylene diphosphonate (Cl2MDP) enclosed in liposomes, caused a delay in the onset and a reduction in the severity of EAU when administered during the “effector” stage of the disease, i.e. 9–11 days after inoculation with retinal antigen. The delay in disease onset was greater when liposomes were mannosylated and was accompanied by a reduction in the overall inflammatory cell infiltrate into the eye and reduced tissue damage. In addition, there was a reduction in the level of expression of MHC Class II antigen and CR3 (ED7) antigen, a marker of macrophage activation, in Cl2MDP-treated animals compared to controls.Conclusion. These results suggest that blood-borne, activated macrophages are major effectors of tissue damage during EAU. Curr. Eye Res. 17: 426–437, 1998.

Effects of macrophage depletion on the induction of histidine decarboxylase by lipopolysaccharide, interleukin 1 and tumour necrosis factor.

1. Our previous work has shown that injection into mice of lipopolysaccharide (LPS) and the cytokines interleukin 1 (IL-1) and tumour necrosis factor (TNF) induces histidine decarboxylase (HDC), the enzyme forming histamine, in various tissues such as liver, lung, spleen and bone marrow, but not in the blood. The induction of HDC also occurs in nude mice and mast cell-deficient mice. On the other hand, haematopoietic cytokines such as IL-3, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage CSF (GM-CSF) only induce HDC in the haematopoietic organs, i.e. bone marrow and spleen. In the present study, the effect of macrophage depletion on the induction of HDC was examined. 2. On day 1 after a single intravenous injection of a macrophage depletor (liposomes encapsulating dichloromethylene diphosphonate, which is toxic when ingested into macrophages), macrophages were almost completely depleted in the liver and reduced by about 50% in the spleen and bone marrow, but not significantly affected in the lung. On day 3, the degrees of the depletion were similar to those of day 1. In the spleen, macrophages were depleted in the red pulp, and there was a structural destruction. 3. In macrophage-depleted mice, the induction of HDC by LPS, IL-1 alpha or TNF-alpha was not impaired in the liver, and was potentiated in the lung and bone marrow. The induction of HDC was decreased only in the spleen at day 3. 4. HDC was not induced by LPS in the spleen of the adult rat, which is correspondingly inactive in haematopoiesis.5 These results indicate that the major cells in which HDC activity is induced in response to LPS, IL-1 and TNF are not circulating granulocytes, circulating monocytes, T cells derived from thymus, mast cells or phagocytic macrophages. Based on these results, we discuss the possibility that the major cells in which HDC was induced in non-haematopoietic and haematopoietic organs were endothelial cells and haematopoietic precursor cells respectively.

Effects of macrophage depletion at different times after treatment with ethylene dimethane sulfonate (EDS) on the regeneration of Leydig cells in the adult rat.

Testicular macrophages were selectively depleted in the right testes of adult rats by an intratesticular injection of dichloromethylene diphosphonate-containing liposomes (Cl2MDP-lp), whereas the left testes were injected with 0.9% NaCl and served as control. Before or after Leydig cell destruction with ethylene dimethane sulfonate (EDS), treatment with Cl2MDP-lp/NaCl was given at different times to study the requirements of macrophages in the different stages of Leydig cell regeneration. On day 30 after EDS treatment, new Leydig cells were abundant in the left, macrophage-containing testes. However, in the right, macrophage-depleted testes, the number of Leydig cells was related to the time elapsed between EDS treatment and macrophage depletion. When macrophages were depleted on day 10 before or on days 4 or 10 after EDS treatment, new Leydig cells were nearly absent at 30 days. However, when macrophages were depleted on days 16 or 22 after EDS treatment, Leydig cells were found at 30 days, but their numbers were equivalent to the number of Leydig cells that were already present in EDS-treated animals at the time the macrophages were depleted. These results indicate that macrophages are needed for the differentiation of Leydig cells from mesenchymal precursors, as well as for the proliferative activity of the newly formed Leydig cells, possibly through the secretion of essential growth factors.

Effect of macrophage depletion on growth and neovascularization of hamster buccal pouch carcinomas

The effect of macrophage depletion on growth and neovascularization of 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinomas (HBPC) was evaluated by quantitating tritiated thymidine (3[H]TdR) incorporation by tumor cells and microvascular endothelium in light microscopic autoradiographs. Tumors that were depleted of macrophages with systemic hydrocortisone acetate (HA) and intratumor injections of antimacrophage serum (AMS) were examined 7 days after treatment. In control animals 30% of infiltrating host cells were esterase-positive tumor-associated macrophages (TAM) and 28.14% of tumor cells and 14.45% of endothelial cells were 3[H]TdR labelled. Hamsters treated with HA or HA and control serum showed no significant reduction in either the number of TAM or proportion of [3H]TdR labelled tumor of endothelial cells. AMS administered alone had no effect on either the content of TAM or 3[H]TdR labelling. In contrast hamsters treated with HA and AMS showed a 54% decrease in TAM and a 50% and 63% reduction in tumor and endothelial cell labelling respectively. These results suggest that growth and neovascularization of these tumors is mediated in part by macrophages.

The effects of macrophage depletion on the clinical and pathologic expression of experimental allergic encephalomyelitis.

The effects of macrophage depletion on the clinical and pathologic expression of experimental allergic encephalomyelitis.