Physiological and Functional Effects of Dominant Active TCRα Expression in Transgenic Mice.

A T cell receptor (TCR) consists of α- and ß-chains. Accumulating evidence suggests that some TCRs possess chain centricity, i.e., either of the hemi-chains can dominate in antigen recognition and dictate the TCR's specificity. The introduction of TCRα/ß into naive lymphocytes generates antigen-specific T cells that are ready to perform their functions. Transgenesis of the dominant active TCRα creates transgenic animals with improved anti-tumor immune control, and adoptive immunotherapy with TCRα-transduced T cells provides resistance to infections. However, the potential detrimental effects of the dominant hemi-chain TCR's expression in transgenic animals have not been well investigated. Here, we analyzed, in detail, the functional status of the immune system of recently generated 1D1a transgenic mice expressing the dominant active TCRα specific to the H2-Kb molecule. In their age dynamics, neither autoimmunity due to the random pairing of transgenic TCRα with endogenous TCRß variants nor significant disturbances in systemic homeostasis were detected in these mice. Although the specific immune response was considerably enhanced in 1D1a mice, responses to third-party alloantigens were not compromised, indicating that the expression of dominant active TCRα did not limit immune reactivity in transgenic mice. Our data suggest that TCRα transgene expression could delay thymic involution and maintain TCRß repertoire diversity in old transgenic mice. The detected changes in the systemic homeostasis in 1D1a transgenic mice, which are minor and primarily transient, may indicate variations in the ontogeny of wild-type and transgenic mouse lines.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)-Specific T Cells and Antibodies in Coronavirus Disease 2019 (COVID-19) Protection: A Prospective Study.

BACKGROUND: During the ongoing coronavirus disease 2019 (COVID-19) pandemic, many individuals were infected with and have cleared the virus, developing virus-specific antibodies and effector/memory T cells. An important unanswered question is what levels of T-cell and antibody responses are sufficient to protect from the infection. METHODS: In 5340 Moscow residents, we evaluated anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin M (IgM)/immunoglobulin G (IgG) titers and frequencies of the T cells specific to the membrane, nucleocapsid, and spike proteins of SARS-CoV-2, using interferon gamma (IFN-γ) enzyme-linked immunosorbent spot (ELISpot) assay. Additionally, we evaluated the fractions of virus-specific CD4+ and CD8+ T cells using intracellular staining of IFN-γ and interleukin 2 followed by flow cytometry. We analyzed the COVID-19 rates as a function of the assessed antibody and T-cell responses, using the Kaplan-Meier estimator method, for up to 300 days postinclusion. RESULTS: We showed that T-cell and antibody responses are closely interconnected and are commonly induced concurrently. Magnitudes of both responses inversely correlated with infection probability. Individuals positive for both responses demonstrated the highest levels of protectivity against the SARS-CoV-2 infection. A comparable level of protection was found in individuals with antibody response only, whereas the T-cell response by itself granted only intermediate protection. CONCLUSIONS: We found that the contribution of the virus-specific antibodies to protection against SARS-CoV-2 infection is more pronounced than that of the T cells. The data on the virus-specific IgG titers may be instructive for making decisions in personalized healthcare and public anti-COVID-19 policies. Clinical Trials Registration. NCT04898140.

Respiratory syncytial virus upregulates IL-33 expression in mouse model of virus-induced inflammation exacerbation in OVA-sensitized mice and in asthmatic subjects.

BACKGROUND: Bronchial asthma (BA) is a chronic disease of the airways. The great majority of BA exacerbations are associated with respiratory viral infections. Recent findings point out a possible role of proinflammatory cytokine interleukin-33 (IL-33) in the development of atopic diseases. Although, little is known about the role of IL-33 in virus-induced BA exacerbations. METHODS: We used mouse models of RSV (respiratory syncytial virus)-induced inflammation exacerbation in OVA-sensitized mice and RSV infection alone in adult animals to characterize expression of il33 in the mouse lungs. Moreover, we studied the influence of il33 knockdown with intranasally administrated siRNA on the development of RSV-induced inflammation exacerbation. In addition, we evaluated the expression of IL33 in the ex vivo stimulated PBMCs from allergic asthma patients and healthy subjects with and without confirmed acute respiratory viral infection. RESULTS: Using mouse models, we found that infection with RSV drives enhanced il33 mRNA expression in the mouse lung. Treatment with anti-il33 siRNA diminishes airway inflammation in the lungs (we found a decrease in the number of inflammatory cells in the lungs and in the severity of histopathological alterations) of mice with RSV-induced inflammation exacerbation, but do not influence viral load. Elevated level of the IL33 mRNA was detected in ex vivo stimulated blood lymphocytes of allergic asthmatics infected with respiratory viruses. RSV and rhinovirus were the most detected viruses in volunteers with symptoms of respiratory infection. CONCLUSION: The present study provides additional evidence of the crucial role of the IL-33 in pathogenesis of RSV infection and virus-induced allergic bronchial asthma exacerbations.

Hormonal function and proliferative activity of thymic cells in humans: immunocytochemical correlations.

OBJECTIVES: The immunocytochemical study of the localization of hormones in thymic cells has been performed to clarify possible correlations of their expression with proliferative activity of thymocytes. METHODS: We used commercial antibodies to serotonin, melatonin, somatostatin, glucagon, gastrin, beta-endorphin and histamine, and ABP or BSP kits for visualization of reaction. Computer image analysis was used to find correlations between hormone production and proliferative activity of thymocytes. RESULTS: Different subpopulations of thymocytes are able to produce hormones: precursors of T-lymphocytes (CD4-CD8-) contain serotonin and melatonin, immature cortical cells (CD4+CD8+) produce only serotonin, mature medullar cells (CD4+CD8-) show immunoreactivity to serotonin, melatonin, beta-endorphin and histamine. The expression of serotonin, somatostatin and gastrin is localized in thymic epithelial cells, formatting Gassal's bodies. Proliferative activity of thymocytes depends from the expression of serotonin and somatostatin in thymic cells. CONCLUSION: The data received testify the expression of different hormones in human thymic cells and showing by this fact high endocrine activity of thymus. The presence of correlations between hormonal expression and cell proliferative activity could be considered as the bright illustration of important role of neuroimmunoendocrine mechanisms in the regulation of local thymic homeostasis.

Tau-protein expression in human blood lymphocytes: a promising marker and suitable sample for life-time diagnosis of Alzheimer's disease.

OBJECTIVES: Taking into account the hypothesis that Alzheimer's disease (AD) might be a systemic disease that affects several tissues in the body, the aim of this study was to try to detect the expression of tau-protein in human peripheral blood lymphocytes (PBL) in patients with AD. MATERIAL AND METHODS: Blood samples were obtained from patients with AD (n=16, age 67-98) and from volunteers without psychoneurological pathology (n=10, age 65-78). PBL were isolated on Ficoll-Paque gradient centrifugation. For cell fixation and permeabilization we used a fixative solution (4% formaldehyde and 0.1% glutaraldehyde) and 0.03% Triton X-100. Immunocytochemical detection of tau-protein was carried out by biotin-streptavidin complex method with tau monoclonal antibody (1:100, clone TAU-2, ICN) and universal immunostaining kit IMMU-MARK (ICN). RESULTS: The expression of tau-protein was shown in PBL in absolute majority of AD patients studied. Only in two healthy volunteers a single lymphocyte from many cells (i.e. a smear) demonstrated a very weak-positive immunostaining to tau-protein CONCLUSION: This first demonstration of clear difference in localization of tau-protein in blood lymphocytes between healthy and sick people testifies to the fact that tau-protein could be considered as a promising marker and blood lymphocytes as a suitable sample for life-time diagnosis of AD.

Interaction between T Lymphocytes and Epithelial Cells in Thymus.

The development (and in some part, the functioning) of T lymphocytes occurs providing their contact with epithelial cells. The interaction between T lymphocytes and epithelium is displayed especially clear in the thymus. Chemotactic signals, the source of which are thymic epithelial cells (TEC), play important role in thymus seeding with precursor cells. It has been found that pairs of adhesion molecules are involved in the formation of contacts between thymocytes and TEC: CD2-CD58, beta1-integrin VLA-4-VCAM-1, beta2-integrin LFA-1-ICAM-1 (the first are given molecules of thymocytes, the second - TEC). T cell differentiation events in the thymus can be united into two groups: 1) transition from precursor cells, deprived receptors for antigen (TCR), to T cells with ability to recognize antigen, and 2) divergence of single trunk of TCR-alpha/beta(+) T cells on two major subpopulations (CD4(+) and CD8(+)) with acquisition of functional maturity by them. The basis of thymocyte interaction with TEC in positive selection of thymocyte clones is recognition them by receptors of complexes of autologous MHC molecules with autologous peptides. Thymocytes are subjected to apoptosis at the all stages of their development provided the absence of contact support with stromal cells and growth factors. The ability of TEC to induce thymocyte apoptosis is revealed in their joint culture. The data presented give clear evidence about interdependency of development and functioning of thymocytes and TEC, as well as about symbiotic character of their interrelations.