Investigation of B lymphocyte subgroups in patients with immune thrombocytopenic purpura

Immune thrombocytopenic purpura is a disease in which autoimmunity plays a role with a decrease in platelet count. Although the remission rate is high after first-line therapy, loss of remission is common and second-line therapy is needed due to relapse. The difference between one patient benefiting from the same treatment and the other not benefiting from the same treatment is not clear. Like all blood cells, lymphocytes originate from stem cells in the bone marrow, produce antigen receptors and develop the characteristic features of mature cells. These mature B and T lymphocytes are called naive lymphocytes. These cells, which migrate from the bone marrow and thymus, migrate to the peripheral lymph organs to complete their transformation and maturation with antigen stimuli. Antigen-stimulated lymphocytes experience clonal expansion, some transform into effector cells that eliminate antigen, while others differentiate into memory cells to play a role in the secondary immune response. Identification of lymphocytes and other leukocytes is done by CD surface antigens in the modern classification system. CD surface markers are monoclonal antibodies that show which cluster the cell has differentiated into. The main role of B lymphocytes (CD45+, CD19+) in the immune system is to recognize immunogenic structures, remember them, and then differentiate into plasma cells that will synthesize antibodies against these antigens. Its migration from the bone marrow to peripheral lymph organs is associated with IgM and IgD synthesis. In a B lymphocyte in the early stages of maturation, CD24 synthesis is increased while IgM+ is detected, while CD27 is negative. With the acquisition of CD27 surface antigen, it is understood that the B lymphocyte differentiates from the naive B lymphocyte to the marginal zone phenotype. Cells with positive CD38 surface antigen are defined as differentiated into memory B lymphocytes. It can be said that the memory cell differentiates into plasmablast with the detection of the loss of IgM and IgD surface antigens and the change of antibodies. In flow cytometry, cells are incubated with antibodies specific for proteins on their surface or inside the cell and bind to antigens. Each specific antibody is labeled with fluorescent dyes such as FITC, PE, PerCP. By evaluating the fluorescent signals given by cells with certain antigens when they encounter a laser beam, it can be determined which specific antigen that cell carries. In our study, we examined the B lymphocyte subgroups of the patients followed up with the diagnosis of ITP with the help of flow cytometry. Our study is a cross-sectional study in which approximately 4 ml of blood samples were taken after routine examinations of patients followed up with the diagnosis of ITP by Tekirdağ Namık Kemal University Hematology Clinic and determined by flow cytometry using DuraClone IM B cells Tube containing B lymphocyte surface antigens. Age, gender, comorbidities, laboratory findings, treatment options and flow cytometry data of the patients were recorded. Statistical analyzes of our study were performed with Jamovi (Version 2.2.5.0) and JASP (Version 0.16.1) programs and the level of significance was considered as 0.05 (p-value) in statistical analysis. 39 patients and 9 healthy control groups were included in the study, and 33 of them were women. The mean age of the patients was 46.58±13.61 (min-max: 20-72 years) years. The control group had the same demographic characteristics as the patient group. When the B lymphocyte subgroups of the patient and control groups were compared; percentages of IgD+CD27+(marginal zone B cell), IgD-IgM-CD27- CD38+High, IgD+IgM+CD27+CD38- (unswitched memory B cell), IgD+IgM+CD27+ CD38+High B lymphocyte subtypes in the patient group were significantly higher, while the percentages of IgD+IgM+CD27-CD38Dim B lymphocyte subtypes were found to be significantly lower in the patient group, they were found to be significantly higher. While naive B cells, which are expected to decrease with age, were found to be significantly higher in ITP patients compared to the healthy population, no significant difference was found in other B cells. While CD27+ memory B cells were found to be low in general in patients treated with rituximab, naive B cells were found to be increased. Similar results were obtained in patients using eltrombopag, and it was thought that previous use of rituximab caused this situation. As expected, marginal zone B cells were found to be significantly lower in patients who underwent splenectomy. Key Words: Immune Thrombocytopenic Purpura, B Cells, CD Markers, CD27