Department of Animal Pharmaceutical Science, Kyushu University of Health and Welfare School of Pharmaceutical Sciences, 1714-1 Yoshino-cho, Nobeoka, Miyazaki 882-8508, Japan.
J Clin Immunol. 2010 Sep;30(5):723-33. doi: 10.1007/s10875-010-9426-1. Epub 2010 May 29.
Human CD93 has a molecular weight of about 100 kDa and is selectively expressed by myeloid cell lineages in peripheral blood (PB) mononuclear cells. Although CD93 was initially identified as a receptor for complement component 1, subcomponent q phagocytosis (C1qRp) involved in the C1q-mediated enhancement of the phagocytosis of various antigens, several recent studies have reported that CD93 is not a receptor for the C1q-mediated enhancement of phagocytosis. The expression patterns of CD93 have been previously investigated in PB mononuclear cells (lymphocytes, monocytes, and granulocytes) from adult PB and neonatal umbilical cord blood (UCB), and the expression of CD93 was not found on lymphocytes from either normal adult PB or neonatal UCB. However, the detection of CD93 expression in neonatal UCB using CD93 monoclonal antibodies (mAbs) that recognize different antigenic epitopes remains poorly understood. In this study, we examined the expression of CD93 on lymphocytes, monocytes, and granulocytes from neonatal UCB using four different types of CD93 mAb detection probes, mNI-11, R139, R3, and X-2, using flow cytometric and western blot analyses. We found that CD93, as defined using all four mAbs, was expressed on monocytes and granulocytes in PB mononuclear cells from adult PB and neonatal UCB. On the other hand, we observed for the first time that the expression of CD93 on lymphocytes in neonatal UCB can only be detected using the mNI-11 mAb, established in our laboratory, and not with commercially available CD93 mAbs (R139, R3, and X-2). However, CD93 expression on lymphocytes from normal adults was not detected using any of the four CD93 mAbs. Two-color flow cytometric analyses showed that the CD93 recognized by mNI-11 mAb was expressed on CD3(+) T lymphocytes (mainly CD4(+) helper T lymphocytes), but not on CD19(+) B lymphocytes or on CD8(+) suppressor/cytotoxic T lymphocytes from neonatal UCB. In addition, CD93 was expressed on CD45RA(+) (naive antigen) lymphocytes from neonatal UCB, but not on CD45RO(+) (memory antigen) lymphocytes from neonatal UCB or on CD45RA(+) and CD45RO(+) lymphocytes from normal adult PB. Three-color flow cytometric analysis showed that CD93 was co-expressed on naive T lymphocytes (CD4(+)CD45RA(+)) from neonatal UCB. In a western blot analysis, the CD93 mAb (mNI-11) immunoprecipitated at a molecular weight of 98 kDa, identified as a CD93 molecule, in the CD4(+)CD45RA(+) cells from neonatal UCB but not from adult PB, similar to the results in the human monocyte-like cell line U937 (human CD93-positive cells). Taken together, these results provide the first direct evidence of a novel/naive cell population (CD4(+)CD45RA(+)CD93(+)) in neonatal UCB that may have an important role in cell biology, transplantation, and immature/mature immune responses.
人 CD93 的分子量约为 100 kDa，选择性地表现在外周血（PB）单核细胞中的髓系细胞谱系中。尽管 CD93 最初被鉴定为补体成分 1 亚组分 q 吞噬作用（C1qRp）的受体，该受体参与 C1q 介导的各种抗原吞噬作用的增强，但最近的几项研究报告表明 CD93 不是 C1q 介导的吞噬作用增强的受体。以前已经在成人 PB 和新生儿脐血（UCB）的 PB 单核细胞（淋巴细胞、单核细胞和粒细胞）中研究了 CD93 的表达模式，并且在正常成人 PB 或新生儿 UCB 的淋巴细胞上均未发现 CD93 的表达。然而，使用识别不同抗原表位的 CD93 单克隆抗体（mAb）在新生儿 UCB 中检测 CD93 的表达仍然知之甚少。在这项研究中，我们使用四种不同类型的 CD93 mAb 检测探针 mNI-11、R139、R3 和 X-2，通过流式细胞术和 Western blot 分析，检查了来自成人 PB 和新生儿 UCB 的单核细胞、单核细胞和粒细胞中 CD93 的表达。我们发现，使用所有四种 mAb 定义的 CD93 在成人 PB 和新生儿 UCB 的 PB 单核细胞中的单核细胞和粒细胞上表达。另一方面，我们首次观察到，新生儿 UCB 中淋巴细胞上的 CD93 表达只能使用我们实验室建立的 mNI-11 mAb 检测到，而不能使用市售的 CD93 mAb（R139、R3 和 X-2）检测到。然而，在任何四种 CD93 mAb 均未检测到正常成年人淋巴细胞上的 CD93 表达。双色流式细胞术分析表明，mNI-11 mAb 识别的 CD93 表达在 CD3(+)T 淋巴细胞（主要是 CD4(+)辅助 T 淋巴细胞）上，但不在 CD19(+)B 淋巴细胞或 CD8(+)抑制/细胞毒性 T 淋巴细胞上来自新生儿 UCB。此外，CD93 表达在新生儿 UCB 的 CD45RA(+)（幼稚抗原）淋巴细胞上，但不在新生儿 UCB 的 CD45RO(+)（记忆抗原）淋巴细胞上，也不在正常成人 PB 的 CD45RA(+)和 CD45RO(+)淋巴细胞上。三色流式细胞术分析表明，CD93 在来自新生儿 UCB 的幼稚 T 淋巴细胞（CD4(+)CD45RA(+))上共表达。在 Western blot 分析中，在来自新生儿 UCB 的 CD4(+)CD45RA(+)细胞中，CD93 mAb（mNI-11）免疫沉淀在分子量为 98 kDa 的位置，鉴定为 CD93 分子，而在成人 PB 中则没有，与人类单核细胞样细胞系 U937（人类 CD93 阳性细胞）的结果相似。总之，这些结果提供了新生儿 UCB 中新型/幼稚细胞群（CD4(+)CD45RA(+)CD93(+))的直接证据，该细胞群可能在细胞生物学、移植和未成熟/成熟免疫反应中发挥重要作用。
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