Flow cytometric analysis of b cell profile in periodontal disease

Abstract

Hallmark of periodontitis has been characterized by dense infiltration of immune cells including B cells and T cells, all of which play critical role in immunopathogenesis of the disease. Most studies of infiltrated B cells in periodontal disease focused on activation stage, and so far there has been no study with a complete analysis of all B cell subsets such as naïve B cells, memory B cells and antibody secreting cells (ASCs). Therefore, we investigated the B cell subsets in inflamed periodontal tissues from patients with severe chronic periodontitis. We confirmed previously described B cell-dominated lesion in periodontitis and T cell-dominated lesion in healthy periodontal tissue. Among three B cell subsets, we found that ASCs (CD19+CD27+CD38+) (58.44 ± 3.79%) were the major cell type in severe chronic periodontitis tissues (n = 21), whereas memory B cells (CD19+CD27+CD38-) (86.59 ± 1.29%) were the major cell type in healthy periodontal tissues (n = 29). Both clinical groups demonstrated low levels of infiltrated naïve B cells (CD19+CD27-CD38-) (less than 7%). At present, it’s not clear if ASCs in periodontitis tissues are plasmablasts or plasma cells. Human leukocyte antigen (HLA)-DR expression was first used to differentiate the two cell types in periodontitis. Our findings clearly showed that the observed infiltrated ASCs were plasma cells (low HLA-DR expression), not plasmablasts (high HLA-DR expression). We also first identified the presence of memory B cells in healthy periodontal tissues. Further study on these B cell subsets should provide a better insight into their role either in periodontal homeostasis or protection.