Department of Research and Development, Institute of Virology, Vaccines and Sera-Torlak, Vojvode Stepe 458, 11221 Belgrade, Serbia.
Immunol Res. 2011 Oct;51(1):97-107. doi: 10.1007/s12026-011-8236-8.
Natural antibodies (NAbs) are present in circulation even before the exposure to antigen and they exert various biological functions. They are polyreactive and mainly represented by immunoglobulin M (IgM), which is the first antibody produced in an ongoing immune response to infection and/or immunization. IgM is always secreted as a polymer with predominant pentameric structure, although other polymeric forms such as hexamer can be also formed. The biological functions of hexameric IgM are still not known and it is proposed that its existence as a NAb could be deleterious. However, the nature of IgM hexamers has not been investigated yet. In this paper, we have tested the expression of natural idiotope and antigenic specificities of pentameric and hexameric IgM polymers originating from sera of patients with Waldenström's macroglobulinemia, as well as patients suffering from recurrent urinary bacterial infections. We demonstrate that although pentameric IgM polymers can exist as natural and immune antibodies, IgM hexamers are exclusively immune and do not exist as NAbs.
天然抗体（NAbs）在接触抗原之前就存在于循环中，它们发挥着各种生物学功能。它们具有多反应性，主要由免疫球蛋白 M（IgM）组成，IgM 是对感染和/或免疫的持续免疫反应中产生的第一种抗体。IgM 总是作为具有主要五聚体结构的聚合物分泌，尽管也可以形成其他聚合形式，如六聚体。六聚体 IgM 的生物学功能尚不清楚，有人提出其作为 NAb 的存在可能是有害的。然而，IgM 六聚体的性质尚未得到研究。在本文中，我们检测了源自瓦尔登斯特伦巨球蛋白血症患者和复发性尿路感染患者血清中的五聚体和六聚体 IgM 聚合物的天然独特型和抗原特异性的表达。我们证明，尽管五聚体 IgM 聚合物可以作为天然和免疫抗体存在，但 IgM 六聚体仅为免疫抗体，不存在作为 NAb。
