Summary of immune findings in fibrotic or progressive sarcoidosis compared to idiopathic pulmonary fibrosis (IPF), as documented in the text
| Fibrotic sarcoidosis or progressive sarcoidosis | IPF | |
| TLR3 polymorphism | Polymorphism Leu412Phe (rs3775291) associated with persistent disease at 2 years [39] | Polymorphism Leu412Phe (rs3775291) associated with disease progression and mortality [38] |
| Transcriptome of lung tissue | Similar to hypersensitivity pneumonitis [46] | Different compared to hypersensitivity pneumonitis [46] |
| Type I IFN signature | Three IFN-stimulated genes upregulated in blood immune cells in more severe compared with milder disease [48] | Enrichment of type I IFN signature in monocytes [50] and a subset of macrophages [51] associated with amount of fibrosis in IPF |
| Monocyte levels | Increased levels in sarcoidosis patients with progressive disease (2-year follow-up) [76] | Increased levels correlate with higher mortality [75] and amount of fibrosis on CT [50] |
| SAA levels | Higher serum levels in fibrotic versus nonfibrotic sarcoidosis [64]; amount of SAA staining in lung tissue correlated with fibrosis [63] | Higher serum levels compared to healthy control [64, 65] |
| CCL-18 | Unstimulated production of CCL-18 in BAL cells increased progressively comparing Scadding stages 1–4 [72] | Serum levels linked to mortality [71] and unstimulated production of CCL-18 in BAL cells higher than control and fibrotic sarcoidosis [72] |
| CD163+ macrophage presence in lung tissue | Increased levels in lung and lymph nodes, linked to progression [80] | Increased levels in lungs [81, 82] |
| Th17 | Th17 cells and IL-17 expression has been shown to be both raised and reduced in sarcoidosis lung, BAL and granuloma [1, 85, 91–99]. PD-1+ Th17 cells increased in blood of fibrotic/progressive sarcoidosis patients [100] | Th17 cells reduced in blood of IPF patients [142]. PD-1+ Th17 increased in blood of IPF [100] |
| Tregs | Lower numbers in BAL [4, 125] and dysfunction in active sarcoidosis [4, 126] | Tregs function impaired in IPF [120] |
| Fibroblastic foci | No difference in transcriptome of fibroblastic foci comparing sarcoidosis and IPF [133] | No difference in transcriptome of fibroblastic foci comparing sarcoidosis and IPF [133] |
BAL: bronchoalveolar lavage; CCL: C-C motif chemokine ligand; CT: computed tomography; PD: programmed cell death; IFN: interferon; IL: interleukin; SAA: serum amyloid antigen; Th: T-helper; TLR: Toll-like receptor; Treg: regulatory T-cell.