Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Microbiology and Immunology

Supervisor

Rodney DeKoter

Abstract

PU.1, Spi-B, and Spi-C are highly related E26 transformation-specific family transcription factors that can bind nearly identical DNA sequences. PU.1 and Spi-B (encoded by Spi1 and Spib respectively) are important for B cell development and function, but the function of Spi-C (encoded by Spic) in B cells is not clear. The objective of this study was to determine PU.1, Spi-B, and Spi-C’s function during B cell development, and during TLR-mediated responses. It was hypothesized that PU.1 and Spi-B were required for positively regulating components of TLR responses, and Spi-C inhibited PU.1 and Spi-B targets. Spi1+/-Spib-/- (PUB) B cells proliferated poorly in response to TLR ligands compared to WT B cells. p50 (encoded by Nfkb1) is required for LPS responsiveness in mice, and PUB B cells expressed reduced Nfkb1 mRNA transcripts and p50 protein. PU.1 and Spi-B were shown to directly regulate Nfkb1 expression required for proper TLR-mediated responses. Next, Spib-/-Spic+/- mice were generated to investigate Spi-C and Spi-B functional redundancy. Spib-/-Spic+/- mice had restored number of B cells in the spleen, and had restored proliferative responses compared to Spib-/- mice. Nfkb1 levels were elevated in Spib-/-Spic+/- B cells compared to Spib-/- B cells. It was demonstrated that Spi-C directly repressed Nfkb1. These results suggest that PU.1 and Spi-B are required for transcriptional activation of Nfkb1, and Spi-C has a negative regulatory role in B cell development and function. Determining the transcriptional regulation of B cell responses has important implications for understanding antibody forming responses, such as those seen in vaccinations.

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