From the Guidelines
Macrophages and T cells, specifically CD4+ T cells, are implicated in the inflammatory response with pulmonary sarcoidosis.
Key Cell Types
- Macrophages: form the central core of granulomas and are accompanied by multinucleated giant cells 1
- T cells: CD4+ T cells play a central role in the immune response, with an accumulation of these cells and release of IL2, followed by the formation of non-caseating granulomas 1
Inflammatory Response
- The inflammatory response in pulmonary sarcoidosis is characterized by the formation of non-caseating granulomas, which are composed of immune cells, including macrophages and T cells 1
- The granulomas are often surrounded by a sparse lymphocytic infiltrate, and the presence of TH1 cytokines, such as interferon, and tumor necrosis factor (TNF) contribute to the inflammatory response 1
Clinical Implications
- The diagnosis of pulmonary sarcoidosis is often established through histological evaluation of tissue granulomas, which typically show well-formed, concentrically arranged layers of immune cells 1
- The clinical manifestations of sarcoidosis are often nonspecific, and the diagnosis may require a multidisciplinary approach, including radiographic testing and clinical evaluation 1
From the Research
Cell Types Implicated in Inflammatory Response
- Macrophages and T lymphocytes play key roles in the inflammatory response in sarcoidosis, with sometimes overlapping cytokine production (i.e., TNFα and IFN-γ) but also with unique mediators that influence the pathologic picture 2
- Alveolar macrophages in patients with sarcoidosis have reduced activity and a decreased level of PPAR-γ, which may contribute to increased inflammation and immune responses 3
- Neutrophils and macrophages have been implicated in the inflammatory response in chronic obstructive pulmonary disease (COPD), but this may not be directly relevant to pulmonary sarcoidosis 4
Inflammatory Pathways in Sarcoidosis
- The inflammatory pathway in sarcoidosis is complex and involves the interplay of intrinsic genetic factors, innate immunity, and adaptive immune responses to external triggers 2
- The distinction between isolated thoracic lymphadenopathy and pulmonary involvement matters, with morbidity often higher and long-term outcomes worse for the latter 5
- The pathogenesis of pulmonary sarcoidosis may differ in important ways from other sarcoidosis manifestations, with recent advances highlighting the role of serum amyloid A and other host factors that contribute to alterations in innate immunity 5
Pulmonary Sarcoidosis
- Pulmonary sarcoidosis is characterized by diverse organ system manifestations, a variable clinical course, and a predilection for affecting relatively young adults worldwide 6
- Abnormalities on chest radiographs are detected in 85% to 95% of patients who have sarcoidosis, with approximately 20% to 50% of patients presenting with respiratory symptoms 6