Immunology Unit, Division of Medical Microbiology, National Health Laboratory Service and Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg Hospital, Cape Town, South Africa.
DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa.
BMC Immunol. 2021 Sep 13;22(1):62. doi: 10.1186/s12865-021-00452-6.
Mendelian Susceptibility to Mycobacterial Disease (MSMD) is a primary immunodeficiency (PID) characterised by a predisposition to infection by weakly-pathogenic mycobacteria. In countries with a high prevalence of tuberculosis (TB), individuals with MSMD are also prone to infections by Mycobacterium tuberculosis. Several MSMD-associated genes have been described, all resulting in a disruption of IL-12 and IFN-γ cytokine axis, which is essential for control of mycobacterial infections. An accurate molecular diagnosis, confirmed by phenotypic and functional immune investigations, is essential to ensure that the patient receives optimal treatment and prophylaxis for infections. The aim of this study was to implement a set of functional assays to assess the integrity of the IL-12-IFN-γ cytokine pathways in patients presenting with severe, persistent, unusual and/or recurrent TB, mycobacterial infections or other clinical MSMD-defining infections such as Salmonella.
Blood was collected for subsequent PBMC isolation from 16 participants with MSMD-like clinical phenotypes. A set of flow cytometry (phenotype and signalling integrity) and ELISA-based (cytokine production) functional assays were implemented to assess the integrity of the IL-12-IFN-γ pathway.
The combination of the three assays for the assessment of the integrity of the IL-12-IFN-γ pathway was successful in identifying immune deficits in the IL-12-IFN-γ pathway in all of the participants included in this study.
The data presented here emphasise the importance of investigating PID and TB susceptibility in TB endemic regions such as South Africa as MSMD and other previously described PIDs relating to TB susceptibility may present differently in such regions. It is therefore important to have access to in vitro functional investigations to better understand the immune function of these individuals. Although functional assays alone are unlikely to always provide a clear diagnosis, they do give an overview of the integrity of the IL-12-IFN-γ pathway. It would be beneficial to apply these assays routinely to patients with suspected PID relating to mycobacterial susceptibility. A molecular diagnosis with confirmed functional impairment paves the way for targeted treatment and improved disease management options for these patients.
孟德尔易感性分枝杆菌病（MSMD）是一种原发性免疫缺陷（PID），其特征是易感染弱致病性分枝杆菌。在结核病（TB）高发的国家，MSMD 患者也容易感染结核分枝杆菌。已经描述了几种与 MSMD 相关的基因，所有这些基因都导致 IL-12 和 IFN-γ 细胞因子轴的破坏，这对于控制分枝杆菌感染至关重要。通过表型和功能免疫研究确认的准确分子诊断对于确保患者接受最佳感染治疗和预防至关重要。本研究的目的是实施一系列功能检测，以评估患有严重、持续、不寻常和/或复发性 TB、分枝杆菌感染或其他临床 MSMD 定义性感染（如沙门氏菌）的患者的 IL-12-IFN-γ 细胞因子途径的完整性。
从 16 名具有 MSMD 样临床表型的参与者中采集血液，用于随后分离 PBMC。实施了一组流式细胞术（表型和信号完整性）和 ELISA 为基础（细胞因子产生）的功能检测，以评估 IL-12-IFN-γ 途径的完整性。
用于评估 IL-12-IFN-γ 途径完整性的三种检测方法的组合成功地在本研究中纳入的所有参与者中确定了 IL-12-IFN-γ 途径中的免疫缺陷。
这里呈现的数据强调了在结核病流行地区（如南非）调查 PID 和结核病易感性的重要性，因为 MSMD 和其他以前描述的与结核病易感性相关的 PID 在这些地区可能表现不同。因此，获得体外功能检测对于更好地了解这些个体的免疫功能非常重要。尽管功能检测本身不太可能总是提供明确的诊断，但它们确实提供了对 IL-12-IFN-γ 途径完整性的概述。将这些检测常规应用于疑似与分枝杆菌易感性相关的 PID 患者将是有益的。具有确认的功能障碍的分子诊断为这些患者开辟了靶向治疗和改善疾病管理的途径。
