RESUMO
OBJECTIVES: This study aimed to compare permanent pacemaker implantation (PPMI) rates among patients undergoing Trans-catheter Aortic Valve Implantation (TAVI) with first generation (G1) versus second generation (G2) valves and the impact of PPMI on long-term mortality. BACKGROUND: PPMI is a known adverse event after TAVI. Recently, two novel iterations of valve designs of both the balloon expandable valves (BEV) and self-expanding valves (SEV) were introduced as a second generation valves. METHODS: All patients included in the Israeli multicenter TAVI registry were grouped according to valve type (BEV vs. SEV) and generation (G1 vs. G2). A comparison was made for clinical and outcome indices of patients undergoing TAVI with G1 and G2 in each of the valve systems. RESULTS: A total of 1377 patients were included. The incidence of PPMI did not differ between G1-BEV versus G2-BEV (15.3% vs. 17.4%; p = 0.598) nor between G1-SEV versus G2-SEV (23.4% vs. 20.3%; p = 0.302). Depth of implantation and complete right bundle branch block were independently associated with PPMI post-TAVI in both valve systems. PPMI was not associated with an increased risk for 2-year mortality. CONCLUSIONS: The incidence of PPMI remains a relevant adverse event post-TAVI even when the newer generation valves are used. Since the predictors for PPMI are well established, a standardized approach for the management of conduction disorders is much needed.
Assuntos
Estenose da Valva Aórtica , Próteses Valvulares Cardíacas , Marca-Passo Artificial , Substituição da Valva Aórtica Transcateter , Valva Aórtica/diagnóstico por imagem , Valva Aórtica/cirurgia , Estenose da Valva Aórtica/diagnóstico por imagem , Estenose da Valva Aórtica/cirurgia , Humanos , Estudos Retrospectivos , Fatores de Risco , Substituição da Valva Aórtica Transcateter/efeitos adversos , Resultado do TratamentoRESUMO
A byproduct of the largely stochastic generation of a diverse B-cell specificity repertoire is production of cells that recognize autoantigens. Indeed, recent studies indicate that more than half of the primary repertoire consists of autoreactive B cells that must be silenced to prevent autoimmunity. While this silencing can occur by multiple mechanisms, it appears that most autoreactive B cells are silenced by anergy, wherein they populate peripheral lymphoid organs and continue to express unoccupied antigen receptors yet are unresponsive to antigen stimulation. Here we review molecular mechanisms that appear operative in maintaining the antigen unresponsiveness of anergic B cells. In addition, we present new data indicating that the failure of anergic B cells to mobilize calcium in response to antigen stimulation is not mediated by inactivation of stromal interacting molecule 1, a critical intermediary in intracellular store depletion-induced calcium influx.
Assuntos
Linfócitos B/imunologia , Anergia Clonal , Animais , Humanos , Ativação Linfocitária , Modelos Imunológicos , Transdução de SinaisRESUMO
Ca(2+) acts ubiquitously as a second messenger in transmembrane signal transduction. In lymphocytes, calcium mobilization is triggered by antigen and chemokine receptors, among others, and controls cell functions ranging from proliferation to migration. The primary mechanism of extracellular Ca(2+) entry in lymphocytes is the CRAC influx. STIM1 is a crucial component of the CRAC influx mechanism in lymphocytes, acting as a sensor of low Ca(2+) concentration in the ER and an activator of the Ca(2+) selective channel ORAI1 in the plasma membrane. While STIM1 function has been studied extensively, little is known regarding whether it is differentially expressed and thereby affects the magnitude of calcium mobilization responses. We report here that STIM1 expression differs in murine T and B lymphocytes, and in respective subsets. For example, mature T cells express â¼4 times more STIM1 than mature B cells. Furthermore, we show that through the physiologic range of expression, STIM1 levels determine the magnitude of Ca(2+) influx responses that follow BCR-induced intracellular store depletion. Considered in view of previous reports that differences in amplitude of lymphocyte Ca(2+) mobilization determine alternate biological responses, these findings suggest that differential STIM1 expression may be important determinant of biological responses.
Assuntos
Subpopulações de Linfócitos B/metabolismo , Sinalização do Cálcio/imunologia , Glicoproteínas de Membrana/biossíntese , Subpopulações de Linfócitos T/metabolismo , Animais , Subpopulações de Linfócitos B/imunologia , Canais de Cálcio , Imunofluorescência , Expressão Gênica , Perfilação da Expressão Gênica , Immunoblotting , Imunoprecipitação , Espectrometria de Massas , Glicoproteínas de Membrana/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Molécula 1 de Interação Estromal , Subpopulações de Linfócitos T/imunologiaRESUMO
CD22-deficient mice are characterized by B cell hyperactivity and autoimmunity. We have constructed knock-in CD22-/- mice, expressing an anti-DNA heavy (H) chain (D42), alone or combined with Vkappa1-Jkappa1 or Vkappa8-Jkappa5 light (L) chains. The Ig-targeted mice produced a lupus-like serology that was age- and sex-dependent. High-affinity IgG autoantibodies were largely dependent on the selection of B cells with a particular H/L combination, in which a non-transgenic, endogenous L chain was assembled by secondary rearrangements through the mechanism of receptor editing. Moreover, we present evidence that these secondary rearrangements are very prominent in splenic peripheral B cells. Since CD22 is primarily expressed on the surface of peripheral B cells, we propose a model for the development of a lupus-like autoimmune disease by a combination of peripheral receptor editing and abnormal B cell activation.
Assuntos
Autoanticorpos/imunologia , Autoimunidade/genética , Lúpus Eritematoso Sistêmico/genética , Edição de RNA , Receptores de Antígenos de Linfócitos B/genética , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico/metabolismo , Animais , Afinidade de Anticorpos/imunologia , Linfócitos B/imunologia , Feminino , Rearranjo Gênico do Linfócito B , Tolerância Imunológica/genética , Masculino , Camundongos , Camundongos Transgênicos , Modelos Imunológicos , Mutação , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico/genéticaRESUMO
Anti-DNA knock-in mice serve as models for studying B cell tolerance mechanisms to a ubiquitous antigen. We have constructed six strains of double transgenic (C57BL/6xBALB/c)F1 mice, each expressing an unmutated or somatically mutated anti-DNA heavy (H) chain, combined with one of three different light (L) chains, namely V(kappa)1-J(kappa)1, V(kappa)4-J(kappa)4 and V(kappa)8-J(kappa)5. In vitro analysis of the various Ig H/L chain combinations showed that all had a similar specificity for single-stranded DNA and double-stranded DNA, but that antibodies encoded by the mutated H chain had higher affinities for the autoantigen. None of the targeted mouse strains exhibited significant levels of serum anti-DNA activity. However, while B cells from mice carrying the V(kappa)1-J(kappa)1 transgenic L chains were tolerized almost exclusively by L chain receptor editing in an affinity-independent manner, the mice expressing V(kappa)8-J(kappa)5 L chains have utilized affinity-dependent clonal anergy as their sole mechanism of B cell tolerance. V(kappa)4-J(kappa)4 targeted mice exhibited an intermediate phenotype with respect to these two mechanisms of B cell tolerance. Our results suggest that receptor editing is the preferred mechanism of B cell tolerance and that the efficiency of L chain editing is directly related to the number of available J(kappa) segments on the expressed V(kappa) allele.
Assuntos
Anticorpos Antinucleares/genética , Autoantígenos/imunologia , DNA/imunologia , Rearranjo Gênico de Cadeia Pesada de Linfócito B , Rearranjo Gênico de Cadeia Leve de Linfócito B , Cadeias J de Imunoglobulina/genética , Região Variável de Imunoglobulina/genética , Cadeias kappa de Imunoglobulina/genética , Receptores de Antígenos de Linfócitos B/genética , Alelos , Animais , Anticorpos Antinucleares/imunologia , Afinidade de Anticorpos , Especificidade de Anticorpos , Células da Medula Óssea/imunologia , Anergia Clonal , Cruzamentos Genéticos , DNA de Cadeia Simples/imunologia , Feminino , Marcação de Genes , Genes de Imunoglobulinas , Genótipo , Hematopoese , Hibridomas/imunologia , Cadeias J de Imunoglobulina/imunologia , Imunoglobulina M/genética , Imunoglobulina M/imunologia , Região Variável de Imunoglobulina/imunologia , Cadeias kappa de Imunoglobulina/imunologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mieloma Múltiplo/patologia , Receptores de Antígenos de Linfócitos B/imunologia , Transfecção , Células Tumorais Cultivadas/imunologiaRESUMO
We have previously constructed knock-in (C57BL/6xBALB/c) F1 mice, each expressing an anti-DNA heavy (H) chain (D42), combined with one of three different light (L) chains, namely Vkappa1-Jkappa1, Vkappa4-Jkappa4 or Vkappa8-Jkappa5. All of these H/L chain combinations bind DNA with similar affinity and fine specificity. However, while mice carrying Vkappa1-Jkappa1-transgenic L chain were tolerized almost exclusively by L chain receptor editing, the mice expressing Vkappa8-Jkappa5 L chains utilized clonal anergy as their principal mechanism of B cell tolerance. Vkappa4-Jkappa4 targeted mice exhibited an intermediate phenotype. In the present study, these three H/L chain combinations were backcrossed onto the autoimmune NZB/NZW F1 mice. We find that the mechanism of clonal anergy is abrogated in these mice, but that receptor editing is maintained. Moreover, diseased NZB/NZW mice utilize L chain secondary rearrangements for the generation of high-affinity, anti-dsDNA-producing B cells from low-affinity precursors. The edited B cell clones are not deleted or anergized in the autoimmune animal; rather they are selected for activation, class-switching and affinity maturation by somatic mutation. These results suggest that B cell receptor editing plays an important role not only in tolerance induction, but also in generating high-affinity autoreactive B cells in autoimmune diseases.