Sibley Taryn A, Miller Michelle M, Fogle Jonathan E
Department of Population Health and Pathobiology, North Carolina State University College of Veterinary Medicine, Raleigh, NC 27607, USA.
Vet Immunol Immunopathol. 2013 Feb 15;151(3-4):229-34. doi: 10.1016/j.vetimm.2012.11.013. Epub 2012 Nov 30.
The IgG receptors CD16 and CD32 (Fc(γ)RIII and Fc(γ)RII) link the humoral immune response to effector cell immune responses by binding immune complexes. Human intravenous immunoglobulin (hIVIG) consisting of immunoglobulin from pooled donors is reported to block Fc(γ)Rs and has been used to treat a variety of canine autoimmune disorders. Fc(γ)Rs have been poorly described for canine monocytes; therefore, the objectives of this study were to: (1) identify canine monocyte/macrophage Fc(γ)R (CD16 and CD32) expression and (2) demonstrate in vitro hIVIG binding to these receptors. The canine monocyte/macrophage-like cell line (DH82) and monocytes isolated from peripheral blood of healthy dogs were evaluated by flow cytometry (FACS) for CD16 and CD32 expression using commercially available anti-CD16 and anti-CD32 antibodies directed against the human isoforms. The mean percentage of cells expressing CD16 was 55% of DH82 cells and 13% of blood monocytes and the mean percentage of cells expressing CD32 was 85% of DH82 cells and 73% of blood monocytes. Immunoprecipitation of canine DH82 cells lysate using the same anti-CD16 or anti-CD32 antibodies suggested that these anti-human antibodies recognize the canine homologues. To demonstrate Fc(γ)R blockade, cells were incubated with increasing concentrations of hIVIG and then incubated with anti-CD16 or anti-CD32 antibodies. The percentage of CD32 expression decreased in a concentration dependent fashion in DH82 cells and blood monocytes after incubation with increasing concentrations of IVIG, suggesting that hIVIG was binding to CD32 and inhibiting anti-CD32 antibody binding. The same results were not demonstrated with anti-CD16 antibody. We believe this is the first report to demonstrate Fc(γ) receptors CD16 and CD32 expression on canine monocytes and in vitro CD32 binding by human IgG, which may represent one of the immunomodulatory mechanisms of hIVIG.
免疫球蛋白G（IgG）受体CD16和CD32（Fc(γ)RIII和Fc(γ)RII）通过结合免疫复合物，将体液免疫反应与效应细胞免疫反应联系起来。据报道，由汇集供体的免疫球蛋白组成的人静脉注射免疫球蛋白（hIVIG）可阻断Fc(γ)Rs，并已用于治疗多种犬类自身免疫性疾病。Fc(γ)Rs在犬单核细胞中的描述较少；因此，本研究的目的是：（1）鉴定犬单核细胞/巨噬细胞Fc(γ)R（CD16和CD32）的表达，以及（2）证明hIVIG在体外与这些受体的结合。使用针对人类异构体的市售抗CD16和抗CD32抗体，通过流式细胞术（FACS）评估犬单核细胞/巨噬细胞样细胞系（DH82）和从健康犬外周血中分离的单核细胞的CD16和CD32表达。表达CD16的细胞的平均百分比在DH82细胞中为55%，在血液单核细胞中为13%；表达CD32的细胞的平均百分比在DH82细胞中为85%，在血液单核细胞中为73%。使用相同的抗CD16或抗CD32抗体对犬DH82细胞裂解物进行免疫沉淀，表明这些抗人抗体识别犬类同源物。为了证明Fc(γ)R阻断，将细胞与浓度递增的hIVIG孵育，然后与抗CD16或抗CD32抗体孵育。在与浓度递增的IVIG孵育后，DH82细胞和血液单核细胞中CD32表达的百分比呈浓度依赖性下降，表明hIVIG与CD32结合并抑制抗CD32抗体的结合。抗CD16抗体未显示相同结果。我们认为，这是首次报道证明犬单核细胞上存在Fc(γ)受体CD16和CD32，以及人IgG在体外与CD32结合，这可能代表人静脉注射免疫球蛋白（hIVIG）的免疫调节机制之一。
