Immune cell hyperactivation along with cytokines they overproduce plays an important role in sarcoidosis and related disease pathogenesis. A central place in the immunopathogenesis of sarcoidosis is held by diverse cell-mediated reactions governed by T helper (Th) cell populations including Th17 subsets and relevant signature cytokines. We studied peripheral blood plasma samples of the patients with sarcoidosis (n = 123): 18% with acute and 82% with chronic course. The control group — samples from healthy volunteers (n = 43). T cell subset composition was assessed by flow cytometry. Cytokine concentrations (pg/mL) were measured by multiplex analysis using xMAP technology (Luminex). The level of “classical” Th17 turned out to be significantly reduced in acute vs chronic sarcoidosis: 28.3% vs 33.3% (p = 0.046). The level of “double-positive” Th17 (DP Th17) was significantly increased in chronic and acute vs control group: 31.7% and 34.2% vs 26.2% (p < 0.001 in both cases), without differences patient inter-group; “non-classical” Th17.1 were shown to have significantly reduced level only in chronic vs healthy subjects: 27.9% and 35.9% (p < 0.001). Clinical and laboratory diagnostic characteristics for blood DP Th17 levels in CD45RA-negative Th effector memory cells in sarcoidosis: in acute sarcoidosis vs healthy subjects, they were characterized by sensitivity — 82%; specificity — 71%, whereas in chronic: 67% and 56%, respectively. In patients with sarcoidosis vs healthy subjects were found to have significantly increased level of IL-12 (p70) — 1.3 vs 0.56, p = 0.028; IL-17A — 1.5 vs 0.43, p < 0.001; IFNγ — 4.1 vs 1.1, p < 0.001; TNFα — 21.7 vs 6.7, p < 0.001. Thus, CCR6 + Th17 and DP Th17 subsets and relevant signature cytokines are important in diagnostics of sarcoidosis of varying clinical course: a direct correlation was shown between the level of angiotensin-converting enzyme activity and percentage of memory DP Th17; disease progression vs regression had significantly reduced absolute number of total CD45RA - memory and CM Th17; extrapulmonary manifestations had a significantly increased percentage of DP Th17 CD45RA - and EM DP Th17; in chronic sarcoidosis are significantly increased concentration of IL-17A, IFNγ, IL-12 and positively correlation between IFNγ and the activity of angiotensin-converting enzyme.

Sarcoidosis is an inflammatory disease of unknown etiology, characterized by development of necrosis-free epithelioid cell granulomas, resulting in hyperactivation of various cells of the immune system. The role of humoral mechanisms in the pathogenesis of sarcoidosis is less studied than cell-mediated. It is necessary to study the role of activation or the anergy of the B cell development of immunity in sarcoidosis, the degree of its activity and the characteristics of the clinical course of the disease. Our study was aimed at investigating the characteristics of the B cells subsets in the peripheral blood of patients with chronic sarcoidosis (n = 41), depending on the activity of the disease. The control was peripheral blood samples from healthy volunteers (n = 43). Objective clinical and instrumental criteria, angiotensin converting enzyme (ACE) were used to determine the activity of the disease. Using flow cytometry analysis of peripheral blood cell B cells were determined based on two approaches: expression of IgD/CD38 (“Bm1-Bm5” classification) and IgD/CD27. In patients with sarcoidosis there was a significantly higher relative number of Bm2 "activated" naive cells" (IgD+CD38+) than in conditionally healthy volunteers, 65.38% versus 55,66% (p < 0.001). The relative and absolute contents of eBm5 (IgD-CD38+) and Bm5 (IgD-CD38+) memory cells were significantly lower in the group of patients with sarcoidosis relative to the control group. Relative values: 6.59% versus 13.31%, (p < 0.001), and 3.43% versus 8.49%, (p < 0.001), respectively. It was shown that with an increased level of ACE in the peripheral blood of patients, the number of naive Bm1 cells (IgD+CD38-) was significantly reduced, r = -0.557, p < 0.001. The relative content of memory B cells that did not switch the class of synthesized antibodies (IgD+CD27+) in the group of patients was reduced to 6,25%, and in the control group — 12,95% (p<0.001). The number of memory cells that switched the class of synthesized antibodies (IgD-CD27+) was also significantly reduced in patients with sarcoidosis and amounted to 6.75% versus 16.50% in the control group (p < 0.001). In patients with high levels of ACE, there was an increase in the relative content of naive B cells (IgD+CD27-), r = 0.532, p < 0.001. An inverse relationship was established between the number of memory B cells (IgD+CD27+) and ACE levels, r = -0.565, p < 0.001. These results indicate the important role of the B cell immune response in the pathogenesis of sarcoidosis and make it possible to evaluate the characteristics of the humoral response with various degrees of disease activity.

The current concept of immunopathogenesis of sarcoidosis is based on an exaggerated immune response to a specific unidentified antigen. In recent years, the high Th17-cell plasticity has been shown to play an important role in the pathogenesis of sarcoidosis, along with contribution of Th1. In this study an analysis of Tfh subpopulation composition in peripheral blood of patients with chronic sarcoidosis debut was performed. Electron microscopic analysis of the microbiological component of bronchoalveolar lavage fluid was conducted to identify infectious agents, in order to determine their aetiological significance in patients in the early stages of sarcoidosis. The data obtained indicate a shift in the balance of Tfh cells towards cells with proinflammatory phenotype, which may indicate their active participation in the immunopathogenesis of sarcoidosis. Commensal bacteria representatives of the normal microbiota were observed in bronchoalveolar lavage fluid. Morphological properties of macrophages witnessed for the active manifestation of their phagocytic function.