All ETDs from UAB

Advisory Committee Chair

John D Mountz

Advisory Committee Members

Charles O Elson

Xu Feng

Chander Raman

Document Type

Dissertation

Date of Award

2020

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

IL-23 promotes autoimmune disease, including Th17 CD4 T-cell development and autoantibody (autoAb) production. Here, we show that a deficiency of the p19 component of IL-23 in the autoimmune BXD2 (BXD2-p19−/−) mouse leads to a shift of the follicular T-helper cell program from Tfh-IL-17 to Tfh-IFN-ɣ. Although the germinal center (GC) size and the number of GC B cells remained the same, BXD2-p19−/− mice exhibited a lower class-switch recombination (CSR) in the GC B cells, leading to lower serum levels of IgG2b. Single-cell transcriptomics analysis of GC B cells revealed that while Ifngr1, Il21r and Il4r genes exhibited a synchronized expression pattern with Cxcr5 and plasma cell program genes, Il17ra exhibited a synchronized expression pattern with Cxcr4 and GC program genes. Down-regulation of Ighg2b in BXD2-p19−/− GC B cells was associated with decreased expression of CSR-related novel base excision repair genes that were otherwise predominantly expressed by Il17ra+ GC B cells in BXD2 mice. Together, these results suggest that although IL-23 is dispensable for GC formation, it is essential to promote a population of Tfh-IL-17 cells. IL-23 acts indirectly on Il17ra+ GC B cells to facilitate CSR-related base excision repair genes during the dark zone phase of GC B-cell development.

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