CD4+ CD25+ FoxP3+ regulatory T cells suppress cytotoxicity of CD8+ effector T cells: implications for their capacity to limit inflammatory central nervous system damage at the parenchymal level

<p>Abstract</p> <p>Background</p> <p>CD4⁺CD25⁺forkhead box P3 (FoxP3)⁺regulatory T cells (T reg cells) are known to suppress adaptive immune responses, key control tolerance and autoimmunity.</p> <p>Methods</p> <p>We challenged the role of CD4⁺T reg cells in suppressing established CD8⁺T effector cell responses by using the OT-I/II system <it>in vitro </it>and an OT-I-mediated, oligodendrocyte directed <it>ex vivo </it>model (ODC-OVA model).</p> <p>Results</p> <p>CD4⁺T reg cells dampened cytotoxicity of an ongoing CD8⁺T effector cell attack <it>in vitro </it>and within intact central nervous system tissue <it>ex vivo</it>. However, their suppressive effect was limited by the strength of the antigen signal delivered to the CD8⁺T effector cells and the ratio of regulatory to effector T cells. CD8⁺T effector cell suppression required T cell receptor-mediated activation together with costimulation of CD4⁺T reg cells, but following activation, suppression did not require restimulation and was antigen non-specific.</p> <p>Conclusions</p> <p>Our results suggest that CD4⁺T reg cells are capable of suppressing CD8⁺T effector cell responses at the parenchymal site, that is, limiting parenchymal damage in autoimmune central nervous system inflammation.</p

The Inflammatory Role of Platelets: Translational Insights from Experimental Studies of Autoimmune Disorders

Beyond their indispensable role in hemostasis, platelets have shown to affect the development of inflammatory disorders, as they have been epidemiologically and mechanistically linked to diseases featuring an inflammatory reaction in inflammatory diseases like multiple sclerosis, rheumatoid arthritis and inflammatory bowel disorders. The identification of novel molecular mechanisms linking inflammation and to platelets has highlighted them as new targets for therapeutic interventions. In particular, genetic and pharmacological studies have identified an important role for platelets in neuroinflammation. This review summarizes the main molecular links between platelets and inflammation, focusing on immune regulatory factors, receptors, cellular targets and signaling pathways by which they can amplify inflammatory reactions and that make them potential therapeutic targets

CD4⁺NKG2D⁺ T Cells Exhibit Enhanced Migratory and Encephalitogenic Properties in Neuroinflammation

<div><p>Migration of encephalitogenic CD4⁺ T lymphocytes across the blood-brain barrier is an essential step in the pathogenesis of multiple sclerosis (MS). We here demonstrate that expression of the co-stimulatory receptor NKG2D defines a subpopulation of CD4⁺ T cells with elevated levels of markers for migration, activation, and cytolytic capacity especially when derived from MS patients. Furthermore, CD4⁺NKG2D⁺ cells produce high levels of proinflammatory IFN-γ and IL-17 upon stimulation. NKG2D promotes the capacity of CD4⁺NKG2D⁺ cells to migrate across endothelial cells in an in vitro model of the blood-brain barrier. CD4⁺NKG2D⁺ T cells are enriched in the cerebrospinal fluid of MS patients, and a significant number of CD4⁺ T cells in MS lesions coexpress NKG2D. We further elucidated the role of CD4⁺NKG2D⁺ T cells in the mouse system. NKG2D blockade restricted central nervous system migration of T lymphocytes in vivo, leading to a significant decrease in the clinical and pathologic severity of experimental autoimmune encephalomyelitis, an animal model of MS. Blockade of NKG2D reduced killing of cultivated mouse oligodendrocytes by activated CD4⁺ T cells. Taken together, we identify CD4⁺NKG2D⁺ cells as a subpopulation of T helper cells with enhanced migratory, encephalitogenic and cytotoxic properties involved in inflammatory CNS lesion development.</p> </div

CD4⁺NKG2D⁺ T cells exert pro-migratory, cytolytic and pro-inflammatory properties.

<p>(<b>A</b>) Flow cytometry: The dot plot shows a representative example of NKG2D expression on CD3⁺CD4⁺CD8^-CD56⁻ T cells derived from the peripheral blood of a healthy donor (HD). The bar graph represents the mean frequency of CD4⁺NKG2D⁺ T cells in the peripheral blood of HDs (<i>n</i> = 20), stable RRMS (<i>n</i> = 15) and active RRMS patients (<i>n</i> = 14). (<b>B</b>–<b>E</b>) Mean fluorescence intensity (MFI) of different markers indicative for migratory capacity (<b>B</b>), activation (<b>C</b>), or cytolytic capacity (<b>D</b>, <b>E</b>) of CD4⁺NKG2D⁺ and CD4⁺NKG2D⁻ T cells from the peripheral blood of HDs (n = 6) or active RRMS patients (<i>n</i> = 6). (<b>F</b>) Percentages of naive (CD45RA⁺CD62L⁺), T central memory (Tcm, CD45RA^-CD62L⁺), T effector memory (Tem, CD45RA^-CD62L⁻) and T effector memory RA (Tem-RA, CD45RA⁺CD62L^-) cells in the CD4⁺NKG2D⁺ and CD4⁺NKG2D⁻ T cell compartment assessed by flow cytometry (<i>n</i> = 6 HDs). (<b>G</b>) Carboxyfluorescein succinimidyl ester (CFSE) proliferation assays of CD4⁺NKG2D⁺ T cells and CD4⁺NKG2D⁻ T cells under CD3/CD28, CD3/NKG2D, MOG_35-55 (10 µg/ml or 100 µg/ml), MBP_1-11 or PLP_190-209 stimulation (<i>n</i> = 8 HDs). (<b>H</b>) Intracellular cytokine staining for IFN-γ and IL-17 of CD4⁺NKG2D⁺ and CD4⁺NKG2D⁻ T cells derived from the peripheral blood of HDs (<i>n</i> = 7). The dot plots depict a representative example of IFN-γ- and IL-17-positive cells upon CD3/CD28 stimulation. The bar graphs show the frequencies of IFN-γ or IL-17 positive cells of unstimulated, CD3/CD28- or CD3/NKG2D-stimulated cells. (<b>I</b>) Comparison of the proportions of IFN-γ or IL-17 positive CD3/CD28-stimulated CD4NKG2D⁺ T cells derived from frozen PBMCs of HDs (<i>n</i> = 6) or active RRMS patients (<i>n</i> = 6). *P < 0.05. ns, not significant; unstim., unstimulated.</p