Tsegaye, Aster (MSc, PhD)Girma, Tigist2018-12-042023-11-062018-12-042023-11-062018-06http://etd.aau.edu.et/handle/123456789/14845Background: Mycobacterium tuberculosis (MTB) remains an unresolved threat resulting in great annual loss of life. The role of B cells during the protective immunity to MTB is still unclear. B cells have been described as effector cells in addition to their role as antibody producing cells during disease. Objective: to identify and characterize the frequency of peripheral B-cell subpopulations during active and latent tuberculosis. Methods: A total of 52 participants comprising 16 active untreated pulmonary TB (PTB) cases, 17 Latent Tuberculosis Infection (LTBI), and 19 Healthy Controls (HCs) were enrolled in the study. Peripheral blood samples were collected to do QuantiFERON (QFT) assay to diagnose LTBI and to isolate Peripheral Blood Mononuclear Cells (PBMC). PBMCs were stained with monoclonal antibodies. Expressions Cluster of differentiation (CD) markers was assessed on B cells subsets using multicolor flowcytometry. A difference in the frequency of B cell subsets among the groups was analyzed using the One-way Anova and Kruskal-Wallis tests was used for comparison between two groups. Data is presented as median (Interquartile range) and a P value of less than 0.05% was taken as a statistically significant difference. Results: Tissue-like memory B cells (CD19+CD27-CD21-); p = 0.0024 and class switched memory B cells (CD19+CD27+CD21+ IgM- IgD-); p = 0.0065 had significantly higher proportion in active PTB when compared to LTBI and HCs. On the contrary, resting memory B cells (CD19+CD27+CD21+); p <.0001, non-class switched memory B cells (CD19+CD27+CD21+ IgM+ IgD+); p = 0.0011, marginal zone B cells (MZCs) (CD19+CD27+CD21+IgM+IgD+CD23-); p = <0.0001 and regulatory B cells (Breg) (CD19+CD24hiCD38hiCD5+); p = 0.0043 had significantly lower proportion in active PTB group as compared to LTBI and HCs. There were no statistically significant difference observed in percentage of total B cells (CD19+); p = 02407, Naïve B cells (CD19+CD27-CD21+); p = 0.1156 and activated memory B cells (CD19+CD27+CD21-); p = 0.1134 among the three study groups. Conclusions: The findings of this study showed that B cells markers distinguish active untreated TB cases from LTBI, that indicate B cells phenotype is promising for clinical application as potential biomarker for TB disease and LTBI identification. A large scale longitudinal study is required to confirm and translate this finding into clinically applicable tests.en-USB cells, Tuberculosis, Immuno-phenotypingThesis