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.

Cytokine gene expression in the skin and peripheral blood of atopic dermatitis patients and healthy individuals.

OBJECTIVES: Atopic dermatitis (AD) is an increasingly common, chronic, relapsing, inflammatory skin disease characterized by impaired epidermal barrier function and cutaneous inflammation. The prevalence of AD has steadily increased during the past few decades. The aim of this study was to comparatively investigate cytokine gene expression in the skin and peripheral blood of atopic dermatitis patients and healthy individuals. RESULTS: In the skin of patients with AD, a significant increase of the level of gene expression was observed for interleukin (IL)-2r (p < 0.0023), IL-5 (p = 0.002), IL-6 (p < 0.0023), IL-8 (p = 0.01), IL-12B (p < 0.0023), IL-10 (p < 0.0023), IL-23 (p = 0.002), IL-29 (p < 0.0023), and transforming growth factor beta (tGFbeta) (p < 0.0023) as compared to healthy individuals. In contrast, no difference between AD patients and healthy donors was detected with respect to cytokine gene expression in the peripheral blood. METHODS: Samples of skin and peripheral blood from 48 severe AD patients (SCORAD = 78.5 [57;89], IGA = 4.2 [3,9;4,7]) at the age of 17 to 45 years and 20 healthy donors aged from 19 to 32 years were analyzed for gene expression of cytokines using real-time reverse transcription polymerase chain reaction (RT-PCR). CONCLUSIONS: Activity of markers of chronic inflammation and Th1 immune response in severe AD, namely IL-2r, IL-8, IL-12B, IL-23, IL-29 and TGFbeta, as well as activity of anti-inflammatory IL-5 were predominant in the skin but not in the blood of AD patients.

What the Thymus is Needed for? Intrathymic Events and Their Uniqueness.

In this report we are reviewing principal data on development of T cell lineage in the thymus and some intrathymic factors. The review is concentrated on the main events of T cell intrathymic development and T cell receptor (TCR) formation, thymocyte clone selection and differentiation of T cell subpopulations. Precursor cells migrate into the thymus overcoming hemato-thymic barrier. Once precursor cells have entered "internal space of the thymus" the processes of TCR beta, gamma and delta gene rearrangement are triggered. Then, T precursors choose the particular pathway for further differentiation towards either TCRalpha/beta or TCRgamma/delta bearing cells. Only when cells acquire TCRalpha/beta features they can continue to develop within the thymus, whereas gamma/delta cells emigrate out of it. TCRalpha/beta cells express protoreceptor (complex beta-pre-TCRalpha-CD3) and coreceptors (CD4 and CD8), proliferate and rearrange TCRalpha-chain gene. After TCRalpha-chain gene successful rearrangement the receptor complex TCRalpha/beta-CD3 is expressed on the cell surface. Since the primary antigen-recognizing repertoire contains some useless and harmful (autoreactive) specificities thymocyte population undergo to two-step selection. During the selection clones recognizing any peptides in context of autologous MHC molecules are maintained (positive selection) and those clones recognizing autologous peptides in context of autologous MHC molecules are eliminated (negative selection). At the same time, thymocytes choose between two coreceptor types - CD4 (which has affinity to MHC II) or CD8 (affinity to MHC I). Thymocytes acquiring CD4 coreceptor become precursors helper T cell, and those acquiring CD8 coreceptor differentiate towards cytotoxic T cells. Many of these events are unique, may progress successfully only within the thymus and are managed by factors of thymic microenvironment. The thymic microenvironment includes epithelial and dendritic cells, macrophages, fibroblasts, myeloid and other stromal cells and their products - cytokines, hormones, neuropeptides, molecules of intercellular matrix etc. Each of the intrathymic factors is not thymus specific when considered apart from others, but their combination and spatial organization are unique for this organ and form a kind of "conveyor" which provides optimum conditions for T cell development.

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.