RESUMEN
At present, it is not clear how memory B lymphocytes are maintained over time, and whether only as circulating cells or also residing in particular tissues. Here we describe distinct populations of isotype-switched memory B lymphocytes (Bsm) of murine spleen and bone marrow, identified according to individual transcriptional signature and B cell receptor repertoire. A population of marginal zone-like cells is located exclusively in the spleen, while a population of quiescent Bsm is found only in the bone marrow. Three further resident populations, present in spleen and bone marrow, represent transitional and follicular B cells and B1 cells, respectively. A population representing 10-20% of spleen and bone marrow memory B cells is the only one qualifying as circulating. In the bone marrow, all cells individually dock onto VCAM1+ stromal cells and, reminiscent of resident memory T and plasma cells, are void of activation, proliferation and mobility.
Asunto(s)
Linfocitos B/inmunología , Células de la Médula Ósea/inmunología , Cambio de Clase de Inmunoglobulina , Memoria Inmunológica , Bazo/inmunología , Adyuvantes Inmunológicos/farmacología , Animales , Animales Salvajes/inmunología , Linfocitos B/citología , Linfocitos B/efectos de los fármacos , Células de la Médula Ósea/citología , Ciclo Celular , Proliferación Celular/genética , Regulación de la Expresión Génica/inmunología , Ratones Endogámicos C57BL , Ratones Transgénicos , Receptores de Antígenos de Linfocitos B/genética , Receptores de Antígenos de Linfocitos B/inmunología , Bazo/citología , Células del Estroma/citología , Molécula 1 de Adhesión Celular Vascular/metabolismoRESUMEN
The bone marrow is a central organ of the immune system, which hosts complex interactions of bone and immune compartments critical for hematopoiesis, immunological memory, and bone regeneration. Although these processes take place over months, most existing imaging techniques allow us to follow snapshots of only a few hours, at subcellular resolution. Here, we develop a microendoscopic multi-photon imaging approach called LIMB (longitudinal intravital imaging of the bone marrow) to analyze cellular dynamics within the deep marrow. The approach consists of a biocompatible plate surgically fixated to the mouse femur containing a gradient refractive index lens. This microendoscope allows highly resolved imaging, repeatedly at the same regions within marrow tissue, over months. LIMB reveals extensive vascular plasticity during bone healing and steady-state homeostasis. To our knowledge, this vascular plasticity is unique among mammalian tissues, and we expect this insight will decisively change our understanding of essential phenomena occurring within the bone marrow.
Asunto(s)
Médula Ósea/irrigación sanguínea , Médula Ósea/diagnóstico por imagen , Hematopoyesis , Microscopía Intravital/métodos , Animales , Células de la Médula Ósea/citología , Fémur , Homeostasis , Ratones Endogámicos C57BL , Ratones Transgénicos , Microscopía de Fluorescencia por Excitación Multifotónica , Nicho de Células MadreRESUMEN
Mitogen-activated protein kinase-activated protein kinase 2 (MK2) is a downstream molecule of p38, involved in the production of TNF-alpha, a key cytokine, and an established drug target for many inflammatory diseases. We investigated the role of MK2 in skin inflammation to determine its drug target potential. MK2 deficiency significantly decreased plasma TNF-alpha levels after systemic endotoxin application. Deficient mice showed decreased skin edema formation in chronic 2-O-tetradecanoylphorbol-13-acetate (TPA)-induced irritative dermatitis and in subacute 2,4-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity. Surprisingly, MK2 deficiency did not inhibit edema formation in subacute 2,4-dinitrochlorobenzene (DNCB)-induced contact allergy and even increased TNF-alpha and IL-1beta levels as well as granulocyte infiltration in diseased ears. Ear inflammation in this model, however, was inhibited by TNF-alpha neutralization as it was in the subacute DNFB model. MK2 deficiency also did not show anti-inflammatory effects in acute DNFB-induced contact hypersensitivity, whereas the p38 inhibitor, SB203580, ameliorated skin inflammation supporting a pathophysiological role of p38. When evaluating possible mechanisms, we found that TNF-alpha production in MK2-deficient spleen cells was strongly diminished after TLR stimulation but less affected after T-cell receptor stimulation. Our data suggest that MK2, in contrast to its downstream effector molecule, TNF-alpha, has a rather elusive role in T-cell-dependent cutaneous inflammation.
Asunto(s)
Inflamación , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Piel/patología , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo , Animales , Dermatitis por Contacto , Dinitrofluorobenceno/química , Femenino , Granulocitos/citología , Homocigoto , Ratones , Ratones Endogámicos C57BL , Receptores de Antígenos de Linfocitos T/metabolismo , Piel/enzimología , Acetato de Tetradecanoilforbol/farmacología , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
IL-10 is a potent immunoregulatory and anti-inflammatory cytokine. However, therapeutic trials in chronic inflammation have been largely disappointing. It is well established that IL-10 can inhibit Th1 and Th2 cytokine production via indirect effects on APC. Less data are available about the influence of IL-10 on IL-17 production, a cytokine which has been recently linked to chronic inflammation. Furthermore, there are only few reports about a direct effect of IL-10 on T cells. We demonstrate here that IL-10 can directly interfere with TCR-induced IFN-gamma production in freshly isolated memory T cells in the absence of APC. This effect was independent of the previously described effects of IL-10 on T cells, namely inhibition of IL-2 production and inhibition of CD28 signaling. In contrast, IL-10 did not affect anti-CD3/anti-CD28-induced IL-17 production from memory T cells even in the presence of APC. This might have implications for the interpretation of therapeutic trials in patients with chronic inflammation where Th17 cells contribute to pathogenesis.