Microenvironments in tuberculous granulomas are delineated by distinct populations of macrophage subsets and expression of nitric oxide synthase and arginase isoforms.

Abstract

Macrophages in granulomas are both antimycobacterial effector and host cell for Mycobacterium tuberculosis, yet basic aspects of macrophage diversity and function within the complex structures of granulomas remain poorly understood. To address this, we examined myeloid cell phenotypes and expression of enzymes correlated with host defense in macaque and human granulomas. Macaque granulomas had upregulated inducible and endothelial NO synthase (iNOS and eNOS) and arginase (Arg1 and Arg2) expression and enzyme activity compared with nongranulomatous tissue. Immunohistochemical analysis indicated macrophages adjacent to uninvolved normal tissue were more likely to express CD163, whereas epithelioid macrophages in regions where bacteria reside strongly expressed CD11c, CD68, and HAM56. Calprotectin-positive neutrophils were abundant in regions adjacent to caseum. iNOS, eNOS, Arg1, and Arg2 proteins were identified in macrophages and localized similarly in granulomas across species, with greater eNOS expression and ratio of iNOS/Arg1 expression in epithelioid macrophages as compared with cells in the lymphocyte cuff. iNOS, Arg1, and Arg2 expression in neutrophils was also identified. The combination of phenotypic and functional markers support that macrophages with anti-inflammatory phenotypes localized to outer regions of granulomas, whereas the inner regions were more likely to contain macrophages with proinflammatory, presumably bactericidal, phenotypes. Together, these data support the concept that granulomas have organized microenvironments that balance antimicrobial anti-inflammatory responses to limit pathology in the lungs.

• Authors: Joshua T Mattila, Olabisi O Ojo, Diane Kepka-Lenhart, Simeone Marino, Jin Hee Kim, Seok Yong Eum, Laura E Via, Clifton E Barry 3rd, Edwin Klein, Denise E Kirschner, Sidney M Morris Jr, Philana Ling Lin, Joanne L Flynn
• Journal: Journal of immunology (Baltimore, Md. : 1950) (J Immunol) Vol. 191 Issue 2 Pg. 773-84 (Jul 15 2013) ISSN: 1550-6606 [Electronic] United States
• PMID: 23749634 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, CD
• Antigens, Differentiation, Myelomonocytic
• CD11c Antigen
• CD163 antigen
• CD68 antigen, human
• Leukocyte L1 Antigen Complex
• Protein Isoforms
• Receptors, Cell Surface
• Nitric Oxide Synthase Type II
• Nitric Oxide Synthase Type III
• Arginase

Topics

• Animals
• Antigens, CD (metabolism)
• Antigens, Differentiation, Myelomonocytic (metabolism)
• Arginase (metabolism)
• CD11c Antigen (metabolism)
• Cellular Microenvironment
• Granuloma (immunology)
• Humans
• Leukocyte L1 Antigen Complex (metabolism)
• Lung (microbiology, pathology)
• Macaca
• Macrophages (cytology)
• Mycobacterium tuberculosis (immunology)
• Myeloid Cells
• Neutrophils (metabolism)
• Nitric Oxide Synthase Type II (metabolism)
• Nitric Oxide Synthase Type III (metabolism)
• Protein Isoforms (metabolism)
• Receptors, Cell Surface (metabolism)
• Tuberculosis (immunology, microbiology, pathology)