Department of Epidemiology, University of Washington, Seattle, Washington, USA.
Department of Laboratory Medicine, University of Washington, Seattle, Washington, USA.
Immun Inflamm Dis. 2018 Sep;6(3):392-401. doi: 10.1002/iid3.231. Epub 2018 Jul 4.
Spontaneous interferon-γ (IFNγ) released detected by enzyme-linked immunospot (ELISpot) assays may be a biological phenomenon. Markers of immune activation levels were assessed as correlates of high background among individuals in Kenya.
Couples concordantly seronegative for HIV-1 were enrolled. IFN-γ ELISpot assays were conducted and negative control wells were categorized as having either high or low background (≥50 and <50 SFU/10 peripheral blood mononuclear cells [PBMC], respectively). PBMC were stained for CD4, CD8, and immune activation markers (CD38 and HLA-DR) and analyzed using flow cytometry. Proportions of activated T-cells were compared between those with low and high background by Mann-Whitney U test. Correlates of background SFU and immune activation were assessed using regression models.
Among 58 individuals, 14 (24%) had high background. Frequencies of CD4 CD38 HLA-DR and CD8 CD38 HLA-DR cells were higher in individuals with high background compared to those with low background (P = 0.02). Higher background SFU was associated with history of sexually transmitted infections (P = 0.03), and illness in the past 3 months (P = 0.005), in addition to increased levels of activated CD4 and CD8 cells (P range = 0.008-0.03). Female gender and male circumcision decreased levels of CD4 and CD8 immune activation (P range = 0.002-0.03). Additionally, higher background SFU and activated CD4 and CD8 cells were individually associated with positive ELISpot responses to HIV-1 peptide pools (P range = 0.01-0.03).
These findings suggest that increased basal immune responses may be a biological mechanism contributing to higher background ELISpot SFU. Systematic exclusion of data from individuals with increased background in IFN-γ release assays may bias results in population-based studies.
酶联免疫斑点（ELISpot）检测到的自发性干扰素-γ（IFNγ）释放可能是一种生物学现象。本研究评估了肯尼亚人群中个体高背景的免疫激活标志物作为相关指标。
纳入 HIV-1 血清学均阴性的夫妻。进行 IFNγ ELISpot 检测，并将阴性对照孔分为高背景（≥50 个斑点形成单位[SFU]/10 个外周血单核细胞[PBMC]）和低背景（<50 SFU/10 PBMC）。使用流式细胞术对 PBMC 进行 CD4、CD8 和免疫激活标志物（CD38 和 HLA-DR）染色，并进行分析。使用 Mann-Whitney U 检验比较低背景和高背景个体之间激活 T 细胞的比例。使用回归模型评估背景 SFU 和免疫激活的相关因素。
在 58 名个体中，14 名（24%）具有高背景。与低背景个体相比，高背景个体的 CD4 CD38 HLA-DR 和 CD8 CD38 HLA-DR 细胞频率更高（P=0.02）。更高的背景 SFU 与性传播感染史（P=0.03）和过去 3 个月内的疾病（P=0.005）相关，此外，与激活的 CD4 和 CD8 细胞水平升高相关（P 值范围为 0.008-0.03）。女性和男性包皮环切术降低了 CD4 和 CD8 免疫激活水平（P 值范围为 0.002-0.03）。此外，更高的背景 SFU 和激活的 CD4 和 CD8 细胞与 HIV-1 肽库的 ELISpot 阳性反应单独相关（P 值范围为 0.01-0.03）。
这些发现表明，基础免疫反应增加可能是导致 ELISpot SFU 背景升高的生物学机制。在基于人群的研究中，如果系统地排除 IFNγ 释放试验中背景较高的个体的数据，可能会导致结果产生偏差。
