With the advent of non-culture based methods, researchers are now aware of the presence of a microbiome within the human lung. The constant presence of microorganisms requires a regulated immune system that can differentiate between infectious organisms and non-infectious commensals. B cells in the lungs are a key member of adaptive immunity by producing antigen specific antibodies as well as immune regulatory roles by secreting various cytokines. In this work, we utilized lung and blood samples paired by donor to test the theory that human lungs hold a unique B cell repertoire. By phenotypic analysis, we found a smaller proportion of CD19+, CD20+ B cells in the lung in respect to the blood. Of this initial pool of cells, a significant proportion were class-switched memory B cells (CS Bmem) and a much lower proportion were naïve B cells in the lung. We have also observed a greater proportion of the residency marker CD69 in CD27- B cells and CD27+ Bmems in the lungs. CS Bmem cells from lung or blood were sorted into a B cell culture system to generate monoclonal antibodies to attempt to analyze antigen-antibody binding through a protein array. Finally, we have analyzed the immunoglobulin variable region genes (IgVRGs) of CS Bmem that are CD69+ or CD69-. We have found that diversity from the unmutated common ancestor (UCA) in pulmonary CS Bmem was as similar as those in the blood. However, comparisons by branch length and mean branch to trunk ratios, we observed greater diversity in the lung compared to blood. We observed both gain and loss of CD69 expression within clones shared between the lungs and blood. The work presented here suggests a model where the lung retains specialized, mature Bmems within the tissue by the expression of CD69. Once stimulated by their antigen, the progeny born from the subsequent expansion would not only spread within the tissue, but also be capable of returning to circulation. This would form an expanded B cell presence at the local tissue level as well as in circulation and efficiently prevent the progress of a potential infection.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/45510 |
| Date | 24 January 2023 |
| Creators | Aihara, Fumiaki |
| Contributors | Kepler, Thomas B. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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