[Show abstract][Hide abstract] ABSTRACT: The purpose of this study is to establish a murine embryonic stem cell (mESC) line for isolation of functional ventricular cardiomyocytes (VCMs) and then to characterize the derived VCMs. By crossing the myosin light chain 2v (Mlc2v)-Cre mouse line with the reporter strain Rosa26-yellow fluorescent protein (YFP), we generated mESC lines from these double transgenic mice, in which Cre-mediated removal of a stop sequence results in the expression of YFP under the control of the ubiquitously active Rosa26 promoter specifically in the VCM. After induction of differentiation via embryoid body (EB) formation, contracting YFP(+) cells were detected within EBs and isolated by fluorescence-activated cell sorting. N-cadherin, the cadherin expressed in cardiomyocytes, and the major cardiac connexin (Cx) isoform, Cx43, were detected in the respective adherens and gap junctions in these VCMs. Using current clamp recordings we demonstrated that mESC-derived VCMs exhibited action potential characteristics comparable to those of neonatal mouse VCMs. Real-time intracellular calcium [Ca(2+)](i) imaging showed rhythmic intracellular calcium transients in these VCMs. The amplitude and frequency of calcium transients were increased by isoproterenol stimulation, suggesting the existence of functional β-adrenergic signaling. Moreover, [Ca(2+)](i) oscillations responded to increasing frequencies of external electrical stimulation, indicating that VCMs have functional excitation-contraction coupling, a key factor for the ultimate cardiac contractile performance. The present study makes possible the production of homogeneous and functional VCMs for basic research as well as for cardiac repair and regeneration.
Stem Cell Research 01/2012; 8(1):49-57. · 4.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: CD4(+) T cells differentiate into multiple effector types, but it is unclear how they form memory T cells during infection in vivo. Profiling virus-specific CD4(+) T cells revealed that effector cells with T helper 1 (Th1) or T follicular helper (Tfh) cell characteristics differentiated into memory cells, although expression of Tfh cell markers declined over time. In contrast to virus-specific effector CD8(+) T cells, increased IL-7R expression was not a reliable marker of CD4(+) memory precursor cells. However, decreased Ly6C and T-bet (Tbx21) expression distinguished a subset of Th1 cells that displayed greater longevity and proliferative responses to secondary infection. Moreover, the gene expression profile of Ly6C(lo)T-bet(int) Th1 effector cells was virtually identical to mature memory CD4(+) T cells, indicating early maturation of memory CD4(+) T cell features in this subset during acute viral infection. This study provides a framework for memory CD4(+) T cell development after acute viral infection.
[Show abstract][Hide abstract] ABSTRACT: Mycoplasma pneumoniae (Mp), a common cause of pneumonia, is associated with asthma; however, the mechanisms underlying this association remain unclear. We investigated the cellular immune response to Mp in mice. Intranasal inoculation with Mp elicited infiltration of the lungs with neutrophils, monocytes and macrophages. Systemic depletion of macrophages, but not neutrophils, resulted in impaired clearance of Mp from the lungs. Accumulation and activation of macrophages were decreased in the lungs of MyD88(-/-) mice and clearance of Mp was impaired, indicating that MyD88 is a key signaling protein in the anti-Mp response. MyD88-dependent signaling was also required for the Mp-induced activation of NFκB, which was essential for macrophages to eliminate the microbe in vitro. Thus, MyD88-NFκB signaling in macrophages is essential for clearance of Mp from the lungs.
PLoS ONE 12/2010; 5(12):e14417. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is unclear where within tissues subsets of effector and memory CD8 T cells persist during viral infection and whether their localization affects function and long-term survival. Following lymphocytic choriomeningitis virus infection, we found most killer cell lectin-like receptor G1 (KLRG1)(lo)IL-7R(hi) effector and memory cells, which are long-lived and high proliferative capacity, in the T cell zone of the spleen. In contrast, KLRG1(hi)IL-7R(lo) cells, which appear terminally differentiated and have shorter life spans, were exclusively localized to the red pulp. KLRG1(lo)IL-7R(hi) T cells homed to the T cell zone using pertussis toxin-sensitive chemokine receptors and appeared to contact gp38(+) stromal cells, which produce the chemokines CCL19 and CCL21 and the T cell survival cytokine IL-7. The transcription factors T-bet and B lymphocyte-induced maturation protein-1 controlled effector CD8 T cell splenic migration. Effector CD8 T cells overexpressing T-bet homed to the red pulp, whereas those lacking B lymphocyte-induced maturation protein-1 homed to the T cell zone. Upon memory formation, CD62L(+) memory T cells were predominantly found in the T cell zone, whereas CD62L(-) cells were found in the red pulp. Thus, effector and memory CD8 T cell subset localization within tissues is linked to their differentiation states, and this may identify anatomical niches that regulate their longevity and homeostasis.
The Journal of Immunology 10/2010; 185(9):5315-25. · 5.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Beuneu et al. (2010) report that the amount of antigenic stimulation initially sensed by naive CD8(+) T cells can establish differentiation set points that are stably maintained in clonal progeny to promote functional diversity.
[Show abstract][Hide abstract] ABSTRACT: During viral infection, effector CD8 T cells contract to form a population of protective memory cells that is maintained by IL-7 and IL-15. The mechanisms that control effector cell death during infection are poorly understood. We investigated how short- and long-lived antiviral CD8 T cells differentially used the survival and cell growth pathways PI3K/AKT and JAK/STAT5. In response to IL-15, long-lived memory precursor cells activated AKT significantly better than short-lived effector cells. However, constitutive AKT activation did not enhance memory CD8 T-cell survival but rather repressed IL-7 and IL-15 receptor expression, STAT5 phosphorylation, and BCL2 expression. Conversely, constitutive STAT5 activation profoundly enhanced effector and memory CD8 T-cell survival and augmented homeostatic proliferation, AKT activation, and BCL2 expression. Taken together, these data illustrate that effector and memory cell viability depends on properly balanced PI3K/AKT signaling and the maintenance of STAT5 signaling.
Proceedings of the National Academy of Sciences 09/2010; 107(38):16601-6. · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although most cells are thought to respond to IFNs, there is limited information regarding specific cells that respond in vivo. Viperin is an IFN-induced antiviral protein and, therefore, is an excellent marker for IFN-responsive cells. In this study, we analyzed viperin expression in vivo during acute lymphocytic choriomeningitis virus Armstrong infection, which induces high levels of type I IFNs, and in persistently infected lymphocytic choriomeningitis virus carrier mice, which contain low levels of type I IFNs. Viperin was induced in lymphoid cells and dendritic cells (DCs) during acute infection and highly induced in neutrophils and macrophages. The expression kinetics in neutrophils, macrophages, and T and B cells paralleled IFN-alpha levels, but DCs expressed viperin with delayed kinetics. In carrier mice, viperin was expressed in neutrophils and macrophages but not in T and B cells or DCs. For acutely infected and carrier mice, viperin expression was IFN dependent, because treating type I IFNR knockout mice with IFN-gamma-neutralizing Abs inhibited viperin expression. Viperin localized to the endoplasmic reticulum and lipid droplet-like vesicles in neutrophils. These findings delineate the kinetics and cells responding to IFNs in vivo and suggest that the profile of IFN-responsive cells changes in chronic infections. Furthermore, these data suggest that viperin may contribute to the antimicrobial activity of neutrophils.
The Journal of Immunology 05/2010; 184(10):5723-31. · 5.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Th2 lymphocytes deliver essential signals for induction of asthmatic airway inflammation. We previously found that airway antigen challenge induces recruitment of Gr-1(+) neutrophils prior to the recruitment of Th2 cells. We examined, therefore, whether Gr-1(+) cells contribute to the development of Th2-dependent airway inflammation. Systemic depletion of Gr-1(+) cells using the RB6-8C5 monoclonal antibody reduced Th2 cell recruitment following i.n. antigen challenge. The levels of both MMP-9 and the tissue inhibitor of matrix metalloproteinases-1 mRNA were up-regulated in the lungs of mice 12 h after i.n. antigen challenge. Up-regulation of tissue inhibitor of matrix metalloproteinases-1 was independent of Gr-1(+) cells, whereas up-regulation of MMP-9 RNA and total gelatinolytic activity was dramatically reduced in mice depleted of Gr-1(+) cells. At 24 h after challenge, total lung collagenolytic activity was also up-regulated, in a Gr-1(+) cell-dependent fashion. Systemic inhibition of MMP-8 and MMP-9 reduced the airway recruitment of Th cells, resulting in significantly reduced eosinophilic inflammation. These data suggest that antigen challenge via the airway activates Gr-1(+) cells and consequently MMP to facilitate the recruitment of Th cells in the airway inflammatory response.
European Journal of Immunology 08/2009; 39(8):2281-92. · 4.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: T helper (Th) cells play major roles in orchestrating asthmatic airway inflammation, but the molecular mechanisms controlling Th-cell recruitment to the airways remain incompletely defined. Innate immunity contributes importantly to the recruitment of effector T cells into sites of inflammation. To understand better the role of innate immune signals in the development of airway inflammation, we used a murine model in which lipopolysaccharide (LPS) contaminating the antigen is thought to trigger Toll-like receptor 4 (TLR4). To investigate the importance of the TLR4-signaling pathway in induction of lung inflammation, we compared recruitment of adoptively transferred ovalbumin-specific Th1 and Th2 cells in wild-type and TLR4 mutant (TLR4m) mice after intranasal or aerosol challenge. Intranasal challenge of TLR4m mice with ovalbumin resulted in decreased recruitment of Th1 and Th2 cells compared with that of wild-type mice. The numbers of Th1 and Th2 cells recruited to the airways of TLR4m mice were less profoundly reduced after aerosol ovalbumin challenge. Comparing the effects of altering the dose of ovalbumin with that of LPS suggested that both contribute to the magnitude of the response in wild-type mice. Our findings demonstrate the importance of both antigen and endotoxin acting in a synergistic manner in the development of airway inflammation.
American Journal Of Pathology 06/2006; 168(5):1425-34. · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To investigate mechanisms underlying the late asthmatic response, we developed a murine model using repetitive intratracheal antigen challenge. BALB/c mice sensitized by i.p. injection with ovalbumin+alum were challenged with ovalbumin intratracheally 4 times. The 1st challenge induced early airway obstruction peaking at 30 min but without a late response; however, the 4th challenge caused not only early but also late airway obstruction at 2-8 h. Eosinophils, and CD4+ and CD8+ T lymphocytes were increased in the airway before the 4th but not before the 1st-3rd challenges. The numbers of IgE+/CD117+ (mast) cells were also increased in the lung before the 4th challenge. Levels of Th2 cytokines were also increased in the airway. Daily administration of dexamethasone during the challenge period suppressed all these inflammatory events. Thus, this experimental late asthmatic response is associated with Th2 cytokine production from inflammatory cells recruited as a consequence of the 1st-3rd challenges.
European Journal of Pharmacology 11/2005; 521(1-3):144-55. · 2.59 Impact Factor