Initiation of Immune Responses in Brain Is Promoted by Local Dendritic Cells

Abstract

The contribution of dendritic cells (DCs) to initiating T cell-mediated immune response in and T cell homing into the CNS has not yet been clarified. In this study we show by confocal microscopy and flow cytometry that cells expressing CD11c, CD205, and MHC class II molecules and containing fluorescently labeled, processed Ag accumulate at the site of intracerebral Ag injection. These cells follow a specific pattern upon migrating out of the brain. To track their pathway out of the CNS, we differentiated DCs from bone marrow of GFP-transgenic mice and injected them directly into brains of naive C57BL/6 mice. We demonstrate that DCs migrate from brain to cervical lymph nodes, a process that can be blocked by fixation or pertussis toxin treatment of the DCs. Injection of OVA-loaded DCs into brain initiates a SIINFEKL (a dominant OVA epitope)-specific T cell response in lymph nodes and spleen, as measured by specific tetramer and LFA-1 activation marker staining. Additionally, a fraction of activated SIINFEKL-specific T cells home to the CNS. Specific T cell homing to the CNS, however, cannot be induced by i.v. injection of OVA-loaded DCs alone. These data suggest that brain-emigrant DCs are sufficient to support activated T cells to home to the tissue of DC origination. Thus, initiation of immune reactivity against CNS Ags involves the migration of APCs from nervous tissue to peripheral lymphoid tissues, similarly to that in other organs.

Brain antigens in functionally distinct antigen-presenting cell populations in cervical lymph nodes in MS and EAE

“…EAE was induced by immunization with spinal cord homogenate or myelin oligodendrocyte glycoprotein (MOG) [8][9][10][11][12][13][14][15][16][17][18][19][20][21] in CFA as described [27,28]. Deep and superficial CLN were also isolated from CCR7-deficient (n=4) and wild-type mice (n=4) [29] with chronic EAE, obtained from stock bred at the animal facility of the Max Delbrück Center for Molecular Medicine (Berlin, Germany).…”

“…A single cell suspension was obtained by passing the lymph nodes through a 70-μm gauze. Lymph node cells, 2×10 5 , were seeded into 96-well round-bottomed plates (Nunc) and stimulated with the indicated concentrations of MOG [8][9][10][11][12][13][14][15][16][17][18][19][20][21] , MOG (both from Advanced Biotechnology Center, Imperial College London), recombinant mouse NF-L (rmNF-L) [40], or ovalbumin (Worthington). After 4 days, T cell proliferation was determined by incorporation of [ 3 H]-thymidine for 18 h (Amersham Biosciences) as described [30].…”

“…Two experiments were using C57BL/6 mice in which EAE was induced by injection with MOG 35-55 (n=5-10 per experiment). One additional experiment was using Biozzi ABH mice (n=10) in which EAE was induced by injection with MOG [8][9][10][11][12][13][14][15][16][17][18][19][20][21] . Figure 5 shows a representative experiment, in which we observed dose-dependent T cell proliferation against the immunizing peptide MOG No proliferation against the irrelevant control antigen OVA was seen.…”

“…Drainage of CNS antigens to the CLN may either occur as soluble proteins or within phagocytes [16,47]. We have previously shown that myelin antigen-containing cells in rhesus monkey CLN express the chemokine receptor CCR7 [21], which mediates leukocyte homing to draining lymph nodes.…”

“…Under experimental conditions, dendritic cells activate naïve CD4 + transgenic T cells directed against proteolipid protein (PLP) 139-151 within the CNS [15]. However, the classical view on the initiation of naïve T cell activation holds that antigens or antigencontaining antigen-presenting cells (APC) must be transferred to the brain-draining cervical lymph nodes (CLN) to effectively activate naïve T cells [16,17]. CNS-resident APC subsequently reactivate these antigen-experienced T cells and allow them to exert their effector functions within the target organ [18,19].…”