Original magnification, 200. Previous reports have suggested monocytes, macrophages, and neutrophils as potent cellular sources of proangiogenic MMP-9 during inflammation.19 In the present study, however, IHC analysis, zymography, and flow cytometry all revealed that in both na?ve mice and infected mice MMP-9 was colocalized almost exclusively with Gr-1bright cells, with minimal MMP-9 expression in Gr-1int monocytes/DC even after neutrophil depletion (see Supplemental Figure S1 at = 10 mice; 0.02). (left) and infected (right) mice. F. Spleen cells from na?ve mice (left graphs) and day 28 infected mice (right graphs) were stained for Gr-1 and intracellular MMP-9 (upper graphs) or an isotype control mAb (ISO; lower graphs) and examined by flow cytometry. Oval gates represent Gr-1bright MMP-9+ cells and show representative frequency. Rectangular gates represent Gr-1dull/neg cells, including monocytes. G. Spleen cells from infected mice treated with isotype control (left graphs) or 1A8 (right graphs) and stained and gated for Gr-1/ISO and MMP-9/ISO as in F. The percentage of Gr-1dull monocytes/DC expressing MMP-9 was 0.4 0.1 in ISO-treated infected mice and was 0.3 0.1 in 1A8-depleted mice. mmc1.doc (1.9M) GUID:?D38789B5-7362-46EB-8800-C5310672790F Abstract Progressive splenomegaly is a hallmark of visceral leishmaniasis in humans, canids, and rodents. In experimental murine visceral leishmaniasis, splenomegaly is accompanied by pronounced changes in microarchitecture, including expansion of the red pulp vascular system, neovascularization of the white pulp, and remodeling of the stromal cell populations that define the B-cell and T-cell compartments. Here, we show that Ly6C/G+ (Gr-1+) cells, including neutrophils and inflammatory monocytes, accumulate in the splenic red pulp during infection. Cell depletion using monoclonal antibody against either Ly6C/G+ (Gr-1; RB6) or Ly6G+ (1A8) cells increased parasite burden. In contrast, depletion of Ly6C/G+ cells, but not Ly6G+ cells, halted the progressive remodeling of Meca-32+ and CD31+ red pulp vasculature. Strikingly, neither treatment affected white pulp neovascularization or the remodeling of the fibroblastic reticular cell and follicular dendritic cell networks. These findings demonstrate a previously unrecognized compartment-dependent selectivity to Rabbit Polyclonal to DRD4 the process of splenic vascular remodeling during experimental murine visceral leishmaniasis, attributable to Ly6C+ inflammatory monocytes. Leishmaniasis, caused by Eleutheroside E protozoan parasites (genus and are responsible for visceral leishmaniasis, the most severe form of the disease, which if untreated is almost universally fatal.1 In mouse models, as with human and canine disease, the spleen is the site of chronic infection.2 As infection progresses, marked splenomegaly develops, associated with extensive remodeling of the lymphoid tissue microarchitecture. Elements Eleutheroside E of the marginal zone are either lost or disrupted in their spatial organization,3 and follicular dendritic cells (FDCs) and fibroblastic reticular cells (FRCs), the key stromal elements that underpin B cell follicle integrity and form the T-cell zone conduit system, respectively,4, 5 are progressively denuded. More recently, we and others have demonstrated that, in murine experimental visceral leishmaniasis (EVL)6 and in canine VL,7 there are pronounced changes to the splenic vasculature that accompany splenomegaly. Notably, in EVL, Meca-32+ red pulp vessels are greatly enlarged and show signs of angiogenesis. In the white pulp, neovascularization leads to the appearance of numerous CD31+SMA-1+ vessels that develop coincident with a breakdown in the organization of the FRC and FDC networks.6 Studies in wild-type mice treated with neutralizing antibodies and in tumor necrosis factor (TNF)-deficient mice have implicated the proinflammatory cytokine tumor necrosis factor (which is overexpressed by macrophages and many other cells during EVL) as a mediator of white pulp stromal cell remodeling.3, 4 However, little is known about the regulation of vascular remodeling within the red pulp or neovascularization in the white pulp. Both neutrophils and inflammatory monocytes have recently attracted much interest in the study of leishmaniasis, by acting as a host cells during infection8, 9, 10 and by playing a variety of regulatory roles that affect late stages of both visceral and cutaneous disease.10, 11, 12 More recently, neutrophils Eleutheroside E that express matrix metalloproteinase 9 (MMP-9),13, 14, 15 as well as inflammatory monocytes,16 have been implicated in the regulation of angiogenesis in a variety of experimental models of disease. In the context of EVL, however, it is currently unknown whether either cell population plays a role in the splenic tissue remodeling that occurs during progressive disease. In the present study, therefore, we sought to determine the effects of Eleutheroside E depletion of these cells on the progressive changes to splenic architecture that are characteristic of this disease. With.