Both innate immunity and acquired immunity are involved in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. The induction of Abs that neutralize the virus has been described, and certain Abs against endemic coronaviruses may cross-react with SARS-CoV-2. Detailed mechanisms to protect against the pandemic of SARS-CoV-2 remain unresolved. We previously reported that IgG Fc-binding protein (Fcγbp), a unique, large molecular weight, and mucin-like secretory Fc receptor protein, secreted from goblet cells of human small and large intestine, mediates the transportation of serum IgG onto the mucosal surface. In this review, we show that mucous bronchial gland cells and some goblet cells are immunoreactive for Fcγbp. Fcγbp traps the cross-reactive (both neutralizing and non-neutralizing) IgG bound to the virus and can consequently eliminate the virus from the mucosal surface to decrease viral loads. Fcγbp can also suppress immune overreaction by interfering with Fc-binding by macrophages and competing with complement fixation. Fcγbp secreted from mucin-producing cells of the airway functions as an important anti-infection mucosal defense. The Fcγbp-mediated mechanism can be a key factor in explaining why SARS-CoV-2 is less infective/lethal in children, and may also be involved in the unique Ab response, recurrent infection, and effects of serum therapy and vaccination.

先天免疫和获得性免疫都与严重急性呼吸系统综合症冠状病毒-2 (SARS-CoV-2) 感染有关。已经描述了中和病毒的抗体的诱导，并且某些针对地方性冠状病毒的抗体可能与 SARS-CoV-2 发生交叉反应。防止 SARS-CoV-2 大流行的详细机制仍未解决。我们之前报道过，IgG Fc 结合蛋白 (Fcγbp) 是一种独特的、大分子量的粘蛋白样分泌型 Fc 受体蛋白，由人小肠和大肠的杯状细胞分泌，介导血清 IgG 向粘膜表面的转运。 . 在这篇综述中，我们表明粘液支气管腺细胞和一些杯状细胞对 Fcγbp 具有免疫反应性。Fcγbp 捕获与病毒结合的交叉反应（中和和非中和）IgG，因此可以从粘膜表面清除病毒以减少病毒载量。Fcγbp 还可以通过干扰巨噬细胞与 Fc 结合和与补体结合竞争来抑制免疫过度反应。气道粘蛋白产生细胞分泌的 Fcγbp 作为重要的抗感染粘膜防御。Fcγbp 介导的机制可能是解释为什么 SARS-CoV-2 在儿童中传染性/致死性较低的关键因素，也可能与独特的抗体反应、反复感染以及血清治疗和疫苗接种的效果有关。Fcγbp 还可以通过干扰巨噬细胞与 Fc 结合和与补体结合竞争来抑制免疫过度反应。气道粘蛋白产生细胞分泌的 Fcγbp 作为重要的抗感染粘膜防御。Fcγbp 介导的机制可能是解释为什么 SARS-CoV-2 在儿童中传染性/致死性较低的关键因素，也可能与独特的抗体反应、反复感染以及血清治疗和疫苗接种的效果有关。Fcγbp 还可以通过干扰巨噬细胞与 Fc 结合和与补体结合竞争来抑制免疫过度反应。气道粘蛋白产生细胞分泌的 Fcγbp 作为重要的抗感染粘膜防御。Fcγbp 介导的机制可能是解释为什么 SARS-CoV-2 在儿童中传染性/致死性较低的关键因素，也可能与独特的抗体反应、反复感染以及血清治疗和疫苗接种的效果有关。