Katarzyna Popko

The role of natural killer cells in pathogenesis of autoimmune diseases

There is growing evidence that NK cell-mediated immunoregulation plays an important role in the control of autoimmunity. NK cells are a subset of lymphocytes that generally contribute to innate immunity but have also a great impact on the function of T and B lymphocytes. The major role of NK cells is cytotoxic reaction against neoplastic, infected and autoreactive cells, but they regulatory function seems to play more important role in the pathogenesis of autoimmune diseases. Numerous studies suggested the involvement of NK cells in pathogenesis of such a common autoimmune diseases as juvenile rheumatoid arthritis, type I diabetes and autoimmune thyroid diseases. The defects of NK cells regulatory function as well as cytotoxic abilities are common in patients with autoimmune diseases with serious consequences including HLH hemophagocytic lymphocytosis (HLH) and macrophage activation syndrome (MAS). The early diagnosis of NK cells defect responsible for the loss of the protective abilities is crucial for the prevention of life-threatening complications and implementation of necessary treatment.

Perforin: an important player in immune response

Perforin is a glycoprotein responsible for pore formation in cell membranes of target cells. Perforin is able to polymerize and form a channel in target cell membrane. Many research groups focus on the role of perforin in various diseases, immune response to bacterial and viral infections, immune surveillance and immunopathology. In addition, perforin is involved in the pathogenesis of autoimmune diseases and allogeneic transplant rejection. Natural killer (NK) cells and CD8-positive T-cells are the main source of perforin. However, CD4-positive T-cells are also able to express a low amount of perforin, when classic cytotoxicity is ineffective or disturbed. Polymerized perforin molecules form channels enabling free, non-selective, passive transport of ions, water, small-molecule substances and enzymes. In consequence, the channels disrupt protective barrier of cell membrane and destroy integrity of the target cell. This review will focus on mechanisms of action and structure of perforin. Also, in this review we discuss the problem of abnormal perforin production in diseases such as: hemophagocytic lymphohistiocytosis (HLH), leukemias and lymphomas, infectious diseases and autoimmune diseases. Better understanding of the role of these molecules in health and disease will open a new field of research with possible therapeutic implications.

Delay in the measurement of eosin-5′-maleimide (EMA) binding does not affect the test result for the diagnosis of hereditary spherocytosis.

Abstract Background: The eosin-5′-maleimide (EMA) binding test is a flow cytometric test widely used to detect hereditary spherocytosis (HS). EMA binds to plasma membrane proteins of red blood cells (RBCs), mainly to band 3 protein. The mean fluorescence of EMA-stained RBCs in HS patients is lower when compared with control RBCs due to the decreased amount of target proteins. EMA dye in aqueous solution is sensitive to light and high temperature. Its fluorescence can decrease when exposed to light or ambient temperatures higher than 4°C. The aim of the study was to evaluate the stability of fluorescence readings of EMA-labeled RBCs over a period of 24 h. Methods: The EMA test was performed in peripheral blood from 35 patients with microcytic anemia (five with HS, and 30 without HS). Peripheral blood samples were stained immediately after blood collection and analyzed using a flow cytometer at three time points: 0, after 1 and 24 h of storage at 4°C in the darkness. The results are presented as the percentage of normal control RBCs fluorescence. Flow cytometric studies were performed with Cytomics FC500 (Beckman Coulter, USA). Results: In HS patients the mean result of the test reached 66.72%±9.26% of normal controls, and in non-HS patients the EMA result was 99.48%±5.03% of normal control cells. The results of patients with HS were 66.72%±9.26%, 66.90%±10.24% and 67.86%±11.31% at 0 h, and after 1 and 24 h of storage, respectively. The results obtained from non-HS patients at time 0, after 1 and 24 h of storage reached 99.48%±5.03%, 99.49%±5.34% and 99.78%±6.13%, respectively. There was no difference between the results from each time point in samples from patients with or without HS. Conclusions: Results of the EMA binding test do not depend on storage time of stained samples when stored at 4°C up to 24 h after staining.

Association between the polymorphism A/G at position 49 of exon 1 of the CTLA-4 gene and antithyroid antibody production in children with Hashimoto's thyroiditis.

CTLA-4 gene is considered to be one of the strongest factors determining the predisposition to antithyroid antibody (Ab) production. The aim of the study was to evaluate the association of the polymorphism A/G of exon 1 of CTLA-4 gene and antithyroid Ab level in children with Hashimoto’s thyroiditis (HT). Material and Methods: 45 children with HT (aged 14.9 ± 2, range 8.1–7.9) and 55 healthy controls (aged 14.8 ± 2.34, range 8.0–17.4) were enrolled. Controls were euthyroid and free from any autoimmune disease. CTLA-4 gene (+49)A/G polymorphism was evaluated by a single-strand conformation polymorphism method and restriction fragment-length polymorphism. Results: The frequency of GG genotype in HT children was significantly higher than in controls: 31 vs. 14.5% respectively (p < 0.04, OR = 2.65, CI = 0.99–7.06). Anti-Tg Ab titers were higher in patients homozygous for G allele than with AA genotype. The GG genotype seemed to be protective from hypothyroidism at the moment of HT diagnosis, but this observation was not statistically confirmed. Conclusions: Our study provides the evidence supporting the association between CTLA-4 gene (+49)A/G polymorphism and the susceptibility to HT in Polish children and confirms the existence of a link between (+49)A/G polymorphism and anti-Tg Ab level.

Cytometric analysis of perforin expression in NK cells, CD8+, and CD4+ lymphocytes in children with autoimmune Hashimoto's thyroiditis--a preliminary study.

Abstract Perforin plays an essential role in cytotoxicity of natural killers (NK) and CD8+ lymphocytes. Cytotoxicity of T and NK cells is one of the mechanisms of destruction of cells in Hashimoto’s disease (HD). The aim of this study was analysis of the expression of perforin in CD8+, CD4+, and NK cells and cytotoxic abilities of these cells in children with HD compared to healthy controls. The expression of perforin and surface antigens, as well as cytotoxicity were analyzed with a flow cytometry. Lower expression of perforin in CD8+ and NK was found in HD compared to controls (p=0.01; p=0.004). A significant correlation between perforin expression in CD8+ lymphocytes and in NK was observed (p=0.05). The spontaneous cytotoxicity of NK was significantly higher in HD compared to controls (p=0.04). Our results suggest that perforin plays an important role in the pathogenesis of autoimmune Hashimoto’s thyroiditis.

Recurrent respiratory tract infections in children - analysis of immunological examinations.

Background Paediatric respiratory tract infections are among the most common reasons for preschool and school absences and visits to physicians. The disease mainly involves the upper respiratory tract and is associated with fever, cough, sore throat, and running nose. Children with recurrent respiratory infections (RRI), which are defined as more than six serious diseases a year, are a difficult diagnostic challenge. The aim of this study was to assess immunological deviations in laboratory tests performed in children with RRI. Material and methods In the retrospective study 25 children suffering from recurrent respiratory tract infection, aged 4.1 ±2.3 years, 13 boys and 12 girls, were involved. For all children chemiluminescence of granulocytes and immunophenotyping of lymphocytes from peripheral blood were examined. An immunophenotype of peripheral blood lymphocytes involved evaluation of T cell, B cells, and NK cells, examined with flow cytometry. Results Eleven of the studied children had decreased chemiluminescent response to stimulants, normal response was found for nine children, and five children had an increased result of the test. Five of the 25 children had decreased B cells number, and five had decreased number of T cells including decrease of CD4, as well as CD8 positive cells. Children with decreased chemiluminescence had more frequent neutropaenia than children with normal or increased chemiluminescent response, p < 0.05 (exact Fisher test). Conclusions Recurrent respiratory tract infection could be associated with improper neutrophils response to pathogens, and immunological examination should be performed to find the reason for the increased number of infections in a year.

Flow Cytometry in Detection of Abnormalities of Natural Killer Cell

The population of natural killer (NK) cells is very heterogeneous and plays a role in the immune system. Several NK cells subpopulations are recognized, differing in phenotype, cytokine release and cytotoxic ability. Different expression of biologically relevant molecules on the surface of NK cells may indicate their multiple functions. The activity of NK cells has mainly to do with their cytotoxic nature. A complete analysis of NK cells function requires application of many tests because a defect may be present at different stages of the cytotoxic process, from signal transduction through lysosome degranulation to target cells destruction. Flow cytometry is actually one of the best methods for the identification of NK cells and tracking their defects.

Leptin Receptor in Childhood Acute Leukemias

Ob-R receptor is encoded by db gene and belongs to class I cytokine receptors family. Its expression was observed in hematopoietic CD34+ stem cells, erythropoietic, myeloid and lymphoblastic lineages cell lines and in human leukemic blast cells in lymphomas, acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML). The studies on human bone marrow cells show that JAK/STAT pathway plays a substantial role in signal transduction in young bone marrow cells. The aim of the study was to examine the relationship between leptin receptor expression and the proliferation of neoplastic hematopoietic cells in bone marrow. The study was performed in a total of 57 children of both sexes aged 3 months to 16 years. A group of 46 patients with acute leukemia involved 25 children with ALLB, 11 children with ALLT and 10 children with ANNL. The control group consisted of 11 non-obese children with non-malignant hematological disturbances. The tests were performed on bone marrow samples. The assessments of membrane expression of Ob-R and the antigens determining the phenotype of bone marrow cells were performed using a flow cytometry method. In acute lymphoblastic leukemia, a significant decrease of Ob-R expression on leukemic blasts was observed in comparison with respective populations of normal bone marrow cells. Also in progenitor cells populations a significant decrease of CD34+Ob-R+w ALLT and ALLB was observed in comparison with the cells from normal bone marrow. No statistically significant differences in the percentage of Ob-R+ cells in ANNL bone marrow and in control bone marrow were observed.

Modulatory effect of insulin on T cell receptor mediated calcium signaling is blunted in long lasting type 1 diabetes mellitus

Insulin significantly influences Ca(2+) signals evoked by various stimulants. In type 1 recent onset diabetes mellitus the proliferative response of T cells is significantly decreased. The number of clinical trials exploring the role of anti-CD3 monoclonal antibodies (mAb) as a therapeutic agent in recent onset diabetes mellitus type 1 is increasing last years. Therefore, a better understanding of the interplay between T cell receptor (TCR) dependent Ca(2+) increase, and insulin is of vital clinical significance. The aim of the study was to assess the effect of insulin on TCR evoked Ca(2+) responses in T lymphocytes obtained from healthy volunteers and patients suffering from long lasting diabetes mellitus type 1. Analysis was performed with use of the flow cytometer. We demonstrated that T cells ability to mobilize Ca(2+) was significantly reduced in long lasting diabetes mellitus type 1. Ca(2+) decrease achieved by the long term incubation with anti-CD3 mAb in T cells from healthy volunteers was restored by insulin. Strong interrelationship between baseline Ca(2+) level and plateau phase response to TCR stimulation was observed in the cytoplasm of cells pre-incubated with insulin from both healthy subjects and diabetic patients (r = 0.95, p < 0.0001 and r = 0.94, p < 0.0001, respectively). We postulate the existence of the interplay between TCR mediated activation and insulin. The TCR-insulin interplay is blunted in long lasting diabetes mellitus type 1. These observations may have an important implication for future therapeutic options in diabetes.

Effectiveness of rituximab in nephrotic syndrome treatment

Idiopathic nephrotic syndrome (INS) is a common chronic illness characterized by massive proteinuria and hypo-albuminemia in children. Baseline treatment is 6 month-corticotherapy. In cases of steroid resistant/dependent INS several types of treatment are used, including course of methyloprednisolone “pulses”, alkylating agents, cyclosporin A, levamisole and mycophenolate mofetil. It has been suggested that children with frequently relapsing nephrotic syndrome or steroid-dependent nephrotic syndrome had a significantly longer relapse-free period if rituximab (RTX) treatment was additionally applied. We present a case of a 4.5 boy who due to steroid-sensitive, steroid-dependent nephrotic syndrome has been successfully treated with RTX. Administration of the one dose of Rituximab in the patient caused immediate decrease of CD19/CD20 positive B lymphocyte population. The depletion of B cells has been observed for the next six months. With regard to the fact that RTX treatment may affect patient’s immune response, comprehensive immunodiagnostic has been conducted in a course of the Therapy.