Microbial interactions, B cell immunoregulation, and positron emission detection in murine models of intestinal inflammation

Inflammatory bowel disease (IBD) emerges when the regulation of intestinal immune-microbial homeostasis is compromised by defects or damage to the epithelial or immunological system. Multiple lymphocyte subsets, including T, B, natural killer (NK), and antigen presenting cells, are able to the suppress murine colitis mediated by pathogenic CD4+ T cells in respective in vivo models; however, the mechanisms behind the effectiveness of regulatory populations and the role of microbial taxa in inducing pathogenic or suppressive lymphocyte subsets are not completely understood. Through a series of Galphai2-/- CD4+ T cell adoptive transfer experiments in which accompanied CD8+, T or B cells were genetically deficient in interaction or effector molecules [(CD80, CD86, CD40, MHCI (major histocompatibility complex), MHCII, cd1d, perforin] or lacked T or B cell receptor antigenic variation, this work reveals that B cells function only to present antigen via MHCI to CD8+ T cells to induce a cytotoxic regulatory population capable of suppressing disease.;Furthermore, fungal and bacterial organisms within the intestines were characterized and their influence on shaping regulatory or pathogenic cell populations examined through correlation of oligonucleotide fingerprinting of ribosomal rRNA genes (OFRG) identified taxa and flow cytometry determined lymphocyte numbers in mice with environmental or antibiotic induced microbial alterations. Such analysis revealed three distinct clusters of microorganism consisting of Bacteroides, Enterobacter, and other Firmicutes phylotypes with either positive or negative associations to systemic and intestinal CD4+ T pathogenic and NK and CD8 + T regulatory lymphocyte subsets.;Lastly, the ability of 18F-fluorodeoxyglucose positron emission tomography (FDG PET) to quantifiably and reliably detect intestinal inflammation and monitor response to treatments was demonstrated in the IL10-/- and Galphai2-/- colitic mice through application of an analysis technique devised through our efforts. Experiments also disclosed that FDG PET was correlated to increased glucose uptake in activated CD4+ T cells rather than standard histological assessment scores. Together these studies produce new data which can lead to the development of new therapeutics and diagnostic tests and thereby enhance the quality of life for individuals afflicted by inflammatory bowel disease.