Koch, Meghan AWang, Bingjie2023-04-172023-04-172023-04-172023Wang_washington_0250E_25220.pdfhttp://hdl.handle.net/1773/49946Thesis (Ph.D.)--University of Washington, 2023Breast milk is a key regulator of host-microbiome interactions in early life. In addition to nutrients, breast milk contains cytokines, growth factors, and antibodies, which help shape the composition of the microbiota and regulate infant immunity to gut microbes. Accumulating evidence links breastfeeding with a decreased risk of developing immune-mediated intestinal and metabolic diseases later in life. As such, current WHO guidelines recommend that mothers exclusively breastfeed for the first six months of life. However, this is not always possible for all women and children. While infant formulas are designed to meet the basic nutritional needs of growing infants, they lack certain components of human breast milk. Understanding which components and how these components of breast milk may influence long-term health, can inform the development of treatments or supplements to breast milk to promote the healthy growth and development of neonates, particularly in infants who are not breastfed.Using a mouse model, our lab discovered that mice deficient in breast milk antibodies mount increased mucosal T cell- dependent immune responses, including elevated T follicular helper (Tfh) cells and germinal center (GC) B cells in the gut-draining lymphoid tissues at the time of weaning. This process is driven by microbes as germ-free mice lacking breast milk antibodies do not generate aberrant mucosal Tfh and GC B cell responses. Due to the profound impact of the gut microbiota on the development of the immune system coupled with the lifelong persistence of activated adaptive immune cells, a current paradigm is that inappropriate adaptive immune responses to gut bacteria drive adverse immune and health outcomes in the long-term. To address this, we first investigated whether the elevation in the GC B cell response observed in offspring that did not receive maternal antibodies resulted in differences in the intestinal memory B cells or plasma cell compartment. To supplement these studies, we developed a novel method to isolate and characterize B cell subsets and plasma cells from the intestine. We observed that offspring that did not receive maternal antibodies showed trending increases in memory and plasma B cells in the colon. However, we did not observe differences in serum or fecal antibody quantity of IgA or any other isotype. Additionally, there were no differences in the microbiota-reactivity of IgA or any other isotype generated in offspring that received or did not receive maternal antibodies. In parallel, we also performed functional readouts of the T cell-dependent adaptive immune response seen in offspring that did not receive maternal antibodies. We asked whether maternal antibodies affect the offspring's intestinal microbiota composition and function in the long term. We found equivalent composition, diversity, and abundance of microbes across different parts of the small intestine and colon between offspring that received or did not receive maternal antibodies. Additionally, we found similar susceptibility to the small intestinal pathogen Salmonella typhimurium or colonic pathogen Citrobacter rodentium between offspring that received or did not receive maternal antibodies. Finally, intestinal length and intestinal transit time of offspring that received or did not receive maternal antibodies were equivalent. Finally, as a first step towards translating this research to humans, we comprehensively mapped the relative contributions of all subclasses of antibodies found in the breast milk of a cohort of healthy, lactating women. Overall, my thesis work has contributed to our understanding of the long-term consequences of maternal antibodies on offspring intestinal immunity. This work may inform the development of therapeutics or supplements to formula to foster beneficial relationships with the gut microbiota and promote long-term health.application/pdfen-USCC BYImmunologyMolecular and cellular biologyThesis