Search PubMed⌕ Search

Biomedical subjects

Sabina Rabatić

Publications and source records attributed to Sabina Rabatić.

4 recordsLinked to original sources
PubMed2006

[Regulatory T cells].

Regulatory T-cells are a subset of T cells that have beene extensively studied in modern immunology. They are important for the maintenance of peripheral tolerance, and have an important role in various clinical conditions such as allergy, autoimmune disorders, tumors, infections, and in transplant medicine. Basically, this population has a suppressive effect on the neighboring immune cells, thus contributing to the local modulation and control of immune response. There are two main populations of regulatory T cells - natural regulatory T cells, which form a distinct cellular lineage, develop in thymus and perform their modulatory action through direct intercellular contact, along with the secreted cytokines; and inducible regulatory T cells, which develop in the periphery after contact with the antigen that is presented on the antigen presenting cell, and their primary mode of action is through the interleukin 10 (IL-10) and transforming growth factor beta (TGF-alpha) cytokines. Natural regulatory T cells are activated through T cell receptor after contact with specific antigen and inhibit proliferation of other T cells in an antigen independent manner. One of the major difficulties in the research of regulatory T cells is the lack of specific molecular markers that would identify these cells. Natural regulatory T cells constitutively express surface molecule CD25, but many other surface and intracellular molecules (HLA-DR, CD122, CD45RO, CD62, CTLA-4, GITR, PD-1, Notch, FOXP3, etc.) are being investigated for further phenotypic characterization of these cells. Because regulatory T cells have an important role in establishing peripheral tolerance, their importance is manifested in a number of clinical conditions. In the IPEX syndrome (immunodysregulation, polyendocrinopathy and enteropathy, X-linked), which is caused by mutation in Foxp3 gene that influences the development and function of regulatory T cells, patients develop severe autoimmune reactions that involve autoimmune endocrine disorders (type 1 diabetes, thyroiditis), respiratory and nutritive allergy, eczema and severe infections. In different types of allergy (pollen allergy, dust mite, nutritive allergens, contact hypersensitivity, etc.) and autoimmune diseases (such as rheumatoid arthritis, multiple sclerosis and type 1 diabetes) a lower number or decreased functional capability of regulatory T cells have been described. In inflammatory conditions and infections, this cell population has an important task in restricting immune response and protecting the host from excessive damage. This ability of regulatory T cells can be used by some pathogens (Epstein Barr virus, Mycobacterium tuberculosis, Leishmania major, etc.) and tumor cells to avoid host response and therefore contribute to the development of some pathological conditions. The knowledge gained on the phenotype and function of regulatory T cells could be useful in many medical conditions. In allergy, autoimmune diseases and in transplant procedures in medicine it would be desirable to increase their function, thus to partially suppress the immune system activity. On the other hand, in some infections and tumors, it would be preferable to decrease the activity of regulatory T cells and boost the function of effector T cells. Regulatory T cells comprise a very active field of immunology, therefore monitoring and modulating of their activity is of great potential significance in a broad spectrum of clinical conditions. By developing and standardizing methods for their monitoring, it would be possible to follow additional parameters of certain clinical conditions and possibly utilize them in therapy.

Humans↗
PubMed2003

[MHC tetramers: tracking specific immunity].

In an adaptive immune response, antigen is recognized by two distinct sets of highly variable receptor molecules: (1) immunoglobulins, that serve as antigen receptors on B cells and (2) the antigen-specific receptors on T cells. T cells play important role in the control of infection and in the development of protective immunity. These cells can also mediate anti-tumor effects and, in case of autoimmune syndromes, contribute to the development and pathology of disease. The specificity of T cells is determined by T cell receptors (TCR). Understanding of the success of immune responses requires the direct measurement of antigen-specific T lymphocytes. Cell with major histocompatibility complex (MHC) class I molecules are able to present antigens to antigen-specific CD8+ cytotoxic T lymphocytes. MHC class I molecules present small peptides (epitopes) processed from intracellular antigens such as viruses and intracellular bacteria. MHC class I molecules in humans are designated as human leukocyte antigen (HLA) class I and divided into HLA-A, -B and -C. CD8+ T cells recognize MHC class I molecules and after activation produce proteins that destroy infected cells. MHC class II molecules receive their peptides mainly from extracellular and soluble antigens and present them to the CD4+ T helper cells. A recently described technique that can be used in flow cytometry enables us to quantify ex vivo antigen-specific T cells by binding of soluble tetramer MHC-peptide complexes attached to fluorochrome. Quantitative analyses of antigen-specific T cell populations provide important information on the natural course of immune responses. The interaction of T cell receptors on T lymphocytes with tetrameric MHC-peptide complexes mimics the situation on the cell surface, and allows for reliable binding. Tetramers consist of four biotinylated HLA-peptide epitope complexes bound to streptavidin conjugated with fluorescent dye. Tetramer technology has sensitivity of detection as little as 0.02% of total cytotoxic T cell pool or T helper cell pool (i.e. approximately 1 in 50.000 lymphocytes). The combination of this technology with intracellular cytokine staining methods opens up significantly better ways of studying these cells than previously possible, allowing immunologists to look at their life cycle (activation and proliferation), manner of death (aging and apoptosis) and effector function (cytotoxic potential and cytokine production). MHC tetramers class I have yielded useful insights into in vivo dynamic and function of antigen-specific CD8+ T cells in viral infections, parasitic infections, cancer, autoimmune disease and transplantation. This knowledge is of special interest for immunotherapy, diagnostic monitoring of T cell mediated immunity, and the development of new vaccination strategies. There is some possibility for cell therapy with antigen-specific CD8+ T cells for various diseases including cancer and viral infections. Targeted immunotherapy of selective deletion of auto--or alloreactive T cells with MHC tetramers may be important for the treatment of autoimmune disease, or to prevent the rejection of transplanted organs. The utility of this technique for the immunotherapy in vivo needs to be confirmed and modified in further research. Understanding how antigen-specific cells develop and function in different circumstances and pathologies will be the key to unravelling the secrets of cellular immune system.

CD8-Positive T-Lymphocytes↗
PubMed2002

Immune parameters in hemorrhagic fever with renal syndrome during the incubation and acute disease: case report.

We describe immune parameters in a Croatian soldier who presented with mild flu-like symptoms and interstitial inflammatory infiltrate in the lungs on an X-ray during the incubation phase of hemorrhagic fever with renal syndrome (HFRS). Enzyme-linked immunosorbent assay (ELISA) IgM and polymerase chain reaction (PCR) were negative. Two weeks later, he developed HFRS caused by the Puumala virus. We performed two-color immunofluorescence cytometry with monoclonal antibodies identifying the activation markers on T cells. Serum samples were also examined by enzyme immunoassay (EIA) for the presence of interleukins IL-2 and IL-6 and their soluble receptors (sR). The analysis of early and late activation markers during the period of incubation revealed a small increase in the percentage of helper (CD4+CD25+) T cells and no significant increase in total activated (HLA-DR+TCR+) and cytotoxic (CD8+CD71+) T cells as compared with healthy controls. In the serum, only the concentration of soluble IL-6 receptor was increased. However, when the patient developed HFRS, all activation markers on T cells increased. Concentrations of sIL-2Ralpha and IL-6 remained increased two and six days after HFRS onset, respectively, whereas sIL-6R increased six days after HFRS onset. IL-2 concentration did not change. Our case indicates that rapid, modern diagnostic tools are necessary in the diagnosis of infectious diseases and their differential diagnosis. Immunological tests, which provide information on the patient immune status and especially on early changes in immune parameters, may contribute to the improvement of the diagnosis, prognosis, and therapy of HFRS.

Adult↗