Sputum Cytokine Levels in Patients with Pulmonary Tuberculosis as Early Markers of Mycobacterial Clearance

Sputum and serum from patients with active pulmonary tuberculosis (TB), healthy purified protein derivative-positive adults, and patients with bacterial pneumonia were collected to simultaneously assess local immunity in the lungs and peripheral blood. To determine whether cytokine profiles in sputum from TB patients and control subjects were a reflection of its cellular composition, cytospin slides were prepared in parallel and assessed for the presence of relative proportions of epithelial cells, neutrophils, macrophages, and T cells. Gamma interferon (IFN-γ) in sputum from TB patients was markedly elevated over levels for both control groups. With anti-TB therapy, IFN-γ levels in sputum from TB patients decreased rapidly and by week 4 of treatment were comparable to those in sputum from controls. Further, IFN-γ levels in sputum closely followed mycobacterial clearance. Although detected at fourfold-lower levels, IFN-γ immunoreactivities in serum followed kinetics in sputum. TNF-α, interleukin 8 (IL-8) and IL-6 also were readily detected in sputum from TB patients at baseline and responded to anti-TB therapy. In contrast to IFN-γ, however, TNF-α and IL-8 levels also were elevated in sputum from pneumonia controls. These data indicate that sputum cytokines correlate with disease activity during active TB of the lung and may serve as potential early markers for sputum conversion and response to anti-TB therapy.

本研究收集了活动性肺结核（active pulmonary tuberculosis, TB）患者、结核菌素纯蛋白衍生物（purified protein derivative, PPD）阳性健康成年人以及细菌性肺炎患者的痰液与血清，以同步评估肺部局部免疫与外周血免疫状态。为明确肺结核患者与对照受试者的痰液细胞因子谱是否可反映其痰液的细胞组成，研究同步制备了细胞离心涂片，并检测上皮细胞、中性粒细胞、巨噬细胞及T细胞的相对占比。结果显示，肺结核患者痰液中的γ干扰素（gamma interferon, IFN-γ）水平显著高于两个对照组。接受抗结核治疗后，肺结核患者痰液中的IFN-γ水平迅速下降，至治疗第4周时已与对照组痰液中的水平相当。进一步分析表明，痰液中IFN-γ水平与分枝杆菌清除进程密切相关。尽管血清中IFN-γ的检测水平仅为痰液中的四分之一，但血清IFN-γ的动态变化趋势与痰液一致。此外，肺结核患者基线状态下的痰液中亦可检测到肿瘤坏死因子-α（tumor necrosis factor-α, TNF-α）、白细胞介素8（interleukin 8, IL-8）及IL-6，且其水平会随抗结核治疗发生应答性变化。但与IFN-γ不同的是，肺炎对照组患者的痰液中TNF-α与IL-8水平同样升高。本研究数据表明，痰液细胞因子水平与肺部活动性肺结核的疾病活动度相关，可作为痰液转阴及抗结核治疗应答的潜在早期标志物。