天疱疮患者T-B细胞相互作用的分子机制及CD19hiICAM-1hiB细胞对抗体产生的影响

Pemphigus is an organ-specific autoimmune blistering disease that is characterized by suprabasal blisters in skin and mucous membranes. Pemphigus has two major subtypes, pemphigus vulgaris (PV) and pemphigus foliaceus (PF), which are caused primarily by pathogenic immunoglobulin G (IgG) autoantibodies against desmoglein 3 (Dsg3) and/or desmoglein (Dsg1). The binding between the antibodies and Dsg could cause the activation of protein enzymes or apoptosis of keratinocytes, which leads?to?the?loss?of?cell-cell?adhesion,?further to the clinical blisters?and?erosions. Our group has focused on the blistering diseases for many years. We found that CD4+ T cells play an important role in B cell activation and antibody production, as well as the subclass switching. However, what's the mechanism for the T-B cells interaction, including the activating status of T/B cells and the expression of co-stimulatory molecules? How are B cells activated and differentiated to antibody-secreting B cells? In this study, we try to discover the activation status of CD4+ T cells and B cells in pemphigus patients and the role of co-stimulatory molecules on B cell differentiation and antibody production. Most importantly, we attempt to identify the phenotype, the function and gene expression of CD19hiICAM-1hi B cells which induced via T/B cell incubation in vitro, compared to CD19loICAM-1lo B cells. Furthermore, we use pemphigus mouse model, which transferred with splenocytes from rDsg3 immunized Dsg3-/- mice, to confirm the function of CD19hiICAM-1hi B cells on antibody production, further to determine the role of this B cell population in the disease development. Our project will provide a novel mechanism of multiple molecules participating T-B cells interaction in pemphigus. CD19hiICAM-1hi B cells might firmly related to the antibody production, which involved in the disease induction and development. Our results might also lay the molecular foundation of studying the pathogenesis of antibody-driven autoimmune diseases as well as to screen optimized therapeutic targets in these autoimmune diseases.

天疱疮是危重的大疱性皮肤黏膜疾病，又是自身免疫病的典型。其发病机制尚未完全清楚，但特异性自身抗体仍发挥主要的致病作用。本课题组在以往研究中发现CD4+T细胞在辅助B细胞产生抗体及抗体亚型转换中起着重要的作用。然而，自身反应性T、B细胞相互作用的分子机制，B细胞出现怎样状态的活化和分化，进而产生致病性抗体，均尚未明确。本项目将进行序贯性研究，明确患者外周血T、B细胞的活化状态及共刺激分子的作用机制；重点研究T、B细胞体外培养后诱导的CD19hiICAM-1hiB细胞的表型、功能、基因表达谱，及其对天疱疮特异性抗体产生的影响。通过本次研究，我们将提出在天疱疮的病理状态下，存在多分子参与的T-B细胞间免疫突触作用，通过诱导CD19hiICAM-1hiB细胞形成，产生致病性抗体，参与疾病发生、发展的新理论，并为天疱疮和/或其他以抗体介导为主的自身免疫病的治疗新靶点提供更为可靠的实验依据和分子基础。

按照课题设计，本课题在既往的研究基础上，对天疱疮患者外周血T-B细胞相互作用的分子机制及CD19hi B细胞的特性及其在自身免疫性疾病发病中的作用进行了研究。结果发现天疱疮患者外周血CD4+T与B细胞均处于相对活化的状态，其表面共刺激分子及其配体的表达显著增加，天疱疮患者CD4+ T细胞和B细胞之间的黏附也明显增强。共刺激分子不同程度地参与了CD4+ T细胞通过T-B细胞之间的相互作用促进B细胞产生抗体这一过程，同时也参与了细胞的存活过程。CD19hi B细胞存在于天疱疮患者外周血中，具有活化表型，其表面高表达共刺激分子的受体或配体，易于接受 CD4+ T 细胞的辅助发生相互作用，该群细胞包含有参与抗体产生的细胞,其比例与体外诱导产生及患者血清中的IgG和 IgM具有密切的相关性。通过本研究，我们提出了在天疱疮病理状态下，存在多分子参与的T-B细胞相互作用，通过诱导CD19hi B细胞的形成，产生特异性致病性抗体，参与疾病发生、发展的新理论。为天疱疮治疗新靶点提供更为可靠的实验依据和分子基础。

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