Immune Correlates of Non-Necrotic and Necrotic Granulomas in Pulmonary Tuberculosis: A Pilot Study

Abstract

A granuloma, a pathologic hallmark of tuberculosis (TB), is a complex cellular structure that develops at the site of Mycobacterium tuberculosis (Mtb) infection and is comprised of different immune cell types. Severe pulmonary TB in humans is characterized by the presence of heterogeneous granulomas, ranging from highly cellular to solid/non-necrotic and necrotic lesions, within the lungs. The host-Mtb interactions within the granulomas dictate the containment of Mtb infection or its progression into a necrotic, cavitary disease. However, the immune environment in various granulomas is poorly understood. The myeloid-derived suppressor cells (MDSCs) are key immune cells that regulate the protective versus permissive host responses against Mtb infection. However, their contexture within the lung granulomas remains unclear. In this study, using single and multiplex immunohistochemical staining, we analyzed the distribution of MDSCs, macrophages, CD4+ T cells and their immunometabolic and effector function states in the solid/non-necrotic and necrotic granulomas in patients with active pulmonary TB. We found increased MDSCs with elevated expression of immunosuppressive molecules in the solid/non-necrotic granulomas. In contrast, cells in the solid and necrotic granulomas produced similar levels of IL-6 and IL-10. Our findings suggest that MDSCs are present in solid/non-necrotic granuloma, which may play an essential role in the progression into a necrotic lesion, thus exacerbating disease pathology and transmission.

Reinventing the human tuberculosis (TB) granuloma: Learning from the cancer field

“…In tissue biopsies from lungs or lymph nodes obtained from patients with active pulmonary TB ( 101 , 132 ) or local TB lymphadenitis ( 60 , 133 ), respectively, we have observed that severely impaired immune functions involve down-regulation of perforin and the antimicrobial peptides LL-37 and granulysin that are necessary to kill Mtb via osmotic lysis. Instead, we and others have shown that persistent Mtb infection promotes expansion of CD4+FoxP3+ Tregs ( 60 , 69 , 101 , 134 ), M2-type macrophages ( 133 , 135 ), or Th2 cells ( 136 , 137 ), as well as MDSCs ( 133 , 138 , 139 ) with suppressive or anti-inflammatory functions in granulomatous TB lesions. While CD8+ T cells are not necessarily lower in numbers in gross Mtb-infected tissues such as lung or lymph nodes, CD8+ T cells are particularly scarce in the GME ( 60 , 132 ).…”

“…137), as well as MDSCs (133,138,139) with suppressive or anti-inflammatory functions in granulomatous TB lesions. While CD8+ T cells are not necessarily lower in numbers in gross Mtb-infected tissues such as lung or lymph nodes, CD8+ T cells are particularly scarce in the GME (60,132).…”

Comprehensive Analysis of Disease Pathology in Immunocompetent and Immunocompromised Hosts following Pulmonary SARS-CoV-2 Infection

“…HPA000288, Millipore Sigma, Burlington, MA, USA) followed by Alexa-488 labeled anti-rabbit secondary antibodies (Cat no. ab150077, Abcam, MA, USA), as described previously [ 19 ]. For the mRNA-FISH technique, labeled smRNA-FISH probes (Biosearch Technologies, Dexter, MI, USA) corresponding to specific host genes were added to the top of the sections and processed as described previously [ 19 ].…”

“…ab150077, Abcam, MA, USA), as described previously [ 19 ]. For the mRNA-FISH technique, labeled smRNA-FISH probes (Biosearch Technologies, Dexter, MI, USA) corresponding to specific host genes were added to the top of the sections and processed as described previously [ 19 ]. Images were captured using Axiovert 200 M inverted fluorescence microscope (Zeiss, Oberkochen, Germany) using 20× or 63× oil-immersion objective with Prime sCMOS camera (Photometrics, Tucson, AZ, USA) by Metamorph image acquisition software (Molecular Devices, San Jose, CA, USA), ImageJ software was used for analyses.…”

Iron–Sulfur Clusters toward Stresses: Implication for Understanding and Fighting Tuberculosis

“…Human necrotic granulomas are a pathologic hallmark and one of the main features of the host's immune response to Mtb [25]. The environment inside granulomas is poor in nutrients such as leucine, arginine, tryptophan and phosphate [26][27][28][29].…”