Post COVID-19 Syndrome (PCS) is a complex of various symptoms developing a month or more after the acute phase of the disease. The cases of PCS development among patients with asymptomatic/mild forms are frequently reported; however, the pathogenesis of PCS in this group of patients is still not completely clear. The publications about COVID-19 which were published in online databases from December 2019 to September 2021 are analyzed in this review. According to the analysis, PCS develops on average in 30–60% of patients, mainly among women. Fatigue, shortness of breath, cough, and anosmia were reported as the most common symptoms. The possible association between the described PCS symptoms and brain damage was revealed. We assume the possibility of an alternative course of COVID-19, which develops in genetically predisposed individuals with a stronger immune response, in which it predominantly affects the cells of the nervous system, possibly with the presence of an autoimmune component, which might have similarity with chronic fatigue syndrome or autoimmune disautonomia. Thus, the gender (female) and the presence of anosmia during an asymptomatic or mild course of the disease can be predictive factors for the development of PCS, which can be caused by autoimmune damage to neurons, glia, and cerebral vessels.

Despite the large number of performed studies, the etiology and pathogenesis of sarcoidosis still remain unknown. Most researchers allude to the possible autoimmune or immune-mediated genesis of the disease. This review attempts an integral analysis of currently available information suggesting an autoimmune genesis of sarcoidosis and is divided into four categories: the evaluation of clinical signs described both in patients with sarcoidosis and “classic” autoimmune diseases, the role of triggering factors in the development of sarcoidosis, the presence of immunogenic susceptibility in the development of the disease, and the analysis of cellular and humoral immune responses in sarcoidosis. Studying the etiology and pathogenesis of sarcoidosis will improve diagnostic procedures as well as the prognosis and patients' quality of life.

Sarcoidosis is a systemic granulomatous disease that develops due to the Th1, Th17 and Treg lymphocytes disturbance. There is an assumption, that B cells and follicular T-helper (Tfh) cells may play an important role in this disorder, as well as in several other autoimmune diseases. The aim of this study was to determine CD19+ B cells subset distribution in the peripheral blood and to define disturbance in the circulating Tfh cells subsets in patients with sarcoidosis. The prospective comparative study was performed in 2016–2018, where peripheral blood B cell subsets and circulating Tfh cell subsets were analyzed in 37 patients with primarily diagnosed sarcoidosis and 35 healthy donors using multicolor flow cytometry. In the results of our study we found the altered distribution of peripheral B cell subsets with a predominance of “naïve” (IgD + CD27−) and activated B cell (Bm2 and Bm2′) subsets and a decreased frequency of memory cell (IgD+ CD27+ and IgD− CD27+) in peripheral blood of sarcoidosis patients was demonstrated. Moreover, we found that in sarcoidosis patients there are increased levels of B cell subsets, which were previously shown to display regulatory capacities (CD24+++ CD38+++ and CD5 + CD27−). Next, a significantly higher proportion of CXCR5-expressing CD45RA − CCR7+ Th cells in patients with sarcoidosis in comparison to the healthy controls was revealed, that represents the expansion of this memory Th cell subset in the disease. This is the first study to demonstrate the association between the development of sarcoidosis and imbalance of circulating Tfh cells, especially CCR4− and CXCR3-expressing Tfh subsets. Finally, based on our data we can assume that B cells and Tfh2- and Tfh17-like cells – most effective cell type in supporting B-cell activity, particularly in antibody production – may be involved in the occurrence and development of sarcoidosis and in several other autoimmune conditions. Therefore, we can consider these results as a new evidence of the autoimmune mechanisms in the sarcoidosis development.

According to an analysis of published data, only 20% of patients with the new coronavirus infection develop severe life-threatening complications. Currently, there are no known biomarkers, the determination of which before the onset of the disease would allow assessing the likelihood of its severe course. The purpose of this literature review was to analyze possible genetic factors characterizing the immune response to the new coronavirus infection that could be associated with the expression of angiotension-converting enzyme 2 (ACE-2) and related proteins as predictors of severe Corona virus disease 2019 (COVID-19). We analyzed original articles published in Medline, PubMed and Scopus databases from December 2019 to November 2020. For searching articles, we used the following keywords: New coronavirus infection, Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), COVID-19, severe course, complications, thrombosis, cytokine storm, ACE-2, biomarkers. In total, 3714 publications were selected using the keywords, of which 8 were in congruence with all the criteria. The literature analysis of the association of immunogenic characteristics and the expression of ACE-2 and related proteins with the development of severe COVID-19 revealed following genetic factors: HLA-B*46:01 genotype, CXCR6 gene hypoexpression, CCR9 gene expression, TLR7, rs150892504 mutations in the ERAP2 gene, overexpression of wild-type ACE-2, TMPRSS2 and its different polymorphisms. Genes, associated with the severe course, are more common among men. According to the analysis data, it can be assumed that there are population differences. However, the diagnostic significance of the markers described must be confirmed with additional clinical studies.

Background: The WHO strategy for eradication of tuberculosis (TB) by 2035 (The End TB Strategy) is aimed at an early and precise diagnosis and subsequent effective treatment of TB patients. Currently, there is no gold standard for the diagnosis of latent TB infection. This study evaluated the diagnostic capabilities of a new intradermal test using recombinant TB allergen (Diaskintest) compared with tuberculin skin test (TST) and commercial TB interferon-gamma release assays (IGRAs). Methods: A post-hoc data analysis that involved examining 860 HIV-negative, bacillus Calmette–Guérin (BCG)-vaccinated persons aged 1–65 years who visited the TB health-care institutions of Saint Petersburg to rule out or confirm an active TB was conducted from 2011 to 2016. Results: A high degree of consistency of the Diaskintest results with the enzyme-linked immunospot and QuantiFERON-TB Gold In-Tube test (ELISPOT and QFT) results was observed in the examined pediatric population (n = 696), with a Diaskintest cutoff ≥5 mm: the kappa consistency indices were 1.000 and 0.937, for ELISPOT and QFT, respectively. A high sensitivity of Diaskintest, comparable with the IGRA tests, was observed in patients with a confirmed TB diagnosis in all age groups. The sensitivity of Diaskintest in patients of the TB/MTB + group aged 18 years and older was 88.7%; of ELISPOT, 90.6%; of QFT, 87.0%. The conducted analysis has shown a high concordance of results of the commercial TB tests in adult HIV-negative patients (n = 164) with a Diaskintest cutoff ≥5 mm: the kappa indices were 0.805 and 0.636 (Diaskintest vs. ELISPOT and QFT, respectively) among BCG-vaccinated people. Conclusion: According to the WHO recommendations, replacing the TST by IGRAs is not recommended as a public health intervention in resource-constrained settings because the IGRA tests are more costly and technically complex to conduct than the TST. Diaskintest has comparable complexity to the TST and its performance is close to that of IGRA in a BCG-vaccinated population. Thus, our study demonstrates that replacing the TST by Diaskintest can be recommended as a public health intervention in resource-constrained and universal BCG vaccination settings.