Flow cytometric characterization of brain dendritic cell subsets after murine stroke

Abstract

BackgroundSterile inflammation is a substantial element of post-stroke pathophysiology with the determination of autoimmunity versus tolerance being one of its most important aspects. It is believed that this determination is initiated relatively early after stroke onset by clearing macrophages and migratory dendritic cells (DC). However, the phenotypic differentiation of macrophages and DC is intricate particularly in the disease context. Here, we utilized a set of surface markers used in mucosal immunity research to investigate the involvement of macrophages and DC subpopulations in post-stroke inflammation in mice.FindingsPhotothrombotic stroke induced a significant increase of lineage (CD3, B220, Ly6G and CD49b) negative CD11b+ cells in the brain primarily consisting of F4/80+ macrophages and, to a lesser extent, F4/80-/CD11c-/CD11b+ monocytes and F4/80-/CD11c+ DC. The latter could be differentiated into the classical migratory DC subpopulations (CD11b+ and CD103+), but no CD4 or CD8+ DC were found. Finally, stroke caused a significant increase of CD11b/CD103 double-positive DC in the affected brain hemisphere.ConclusionsThe surface marker combination used in this study allowed a phenotypic differentiation of macrophages and DC subpopulations after stroke, thus providing an important prerequisite to study post-stroke immunity and tolerance.

Antigen Presentation After Stroke

“…+ cells has been reported [9]. Whether these cells will reach the draining lymph nodes to present antigen to T cells remains elusive, but our study of tonsils from patients with stroke, i.e., lymphoid tissue located within the draining pathways of the CNS, showed neural antigens on migratory BDCA1…”

“…Acute brain damage generates a genuine inflammatory reaction triggered by necrotic neuronal cells that leak their content to the extracellular space and trigger strong innate immune responses involving resident microglia and infiltrating leukocytes [4,5]. Notably, antigen-presenting cells (APC) accumulate in the brain parenchyma during the days that follow experimental stroke [6][7][8][9][10]. These cells express major histocompatibility complex (MHC) class II and co-stimulatory molecules, as well as markers of conventional dendritic cells (DCs).…”

Sepsis-associated encephalopathy: a vicious cycle of immunosuppression

“…Monocytes/macrophages Decreasing the number of monocytes; polarization of M2 phenotype; increasing production of IL-10; reducing phagocytic capability [43], [44], [45] Neutrophils Impairment in ROS production; reduction of phagocytosis; shortening life-span as a result of spontaneous apoptosis [43,[46][47][48][49] Dendritic cells Decreasing number of circulating DCs; anergic response to TLR3 and TLR4 stimulations; incapable of priming effective cellular immune response; disturbed infiltration and aberrant phenotypic differentiation [50][51][52][53] T lymphocytes Reducing proportion of peripheral T cells; disturbing response to antigens; polarization of anti-inflammatory phenotypes; inducing imbalance between Tregs and proinflammatory phenotypes of T cells [54][55][56][57][58] sepsis, but they are rarely found in the normal brain [66]. Neutrophils accumulating in the central nervous system jeopardize brain cells by releasing inflammatory cytokines, increasing the activity of myeloperoxidase, and promoting oxidative damage [74].…”

“…Yilmaz and colleagues found that circulating DC precursors underwent transient decrease after acute stroke, which was correlated with the severity of brain injury [51]. Furthermore, disturbed infiltration and aberrant phenotypic differentiation of DCs were also characterized under brain dysfunction [52,53]. However, the precise mechanisms of the dysfunction of DCs and its significance in host immunosuppression remain to be clarified.…”

Depletion of CD11c⁺ Cells Does Not Influence Outcomes in Mice Subjected to Transient Middle Cerebral Artery Occlusion

“…First, we did not assess the time course, detailed location, or number of DC in the mouse brains before or after stroke induction. Several groups have previously done this and described a uniform dynamic of DC infiltration in rodents subjected to focal cerebral ischemia: cDC (defined by CD11b + /CD103 + ) were virtually absent in naive murine brain tissue [31] . In the ischemic core of rat brains, the presence of DC expressing major histocompatibility complex II has been reported as early as a few hours after stroke onset, with a maximum on day 6, but not in animals without stroke [32] .…”