Document Type

Thesis - University Access Only

Award Date

2005

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

Abstract

The neonatal ruminant immune system is susceptible to opportunistic infection due to minimal circulating B cells. This situation is overcome by roughly 6 months of age, when a massive expansion in B cells and hence Antibody (Ab) repertoire has occurred within the ruminant primary lymphoid structure, the ileal Peyer's patch (IPP). Neonatal immunity is obtained passively through milk and colostrum ingestion, and provides temporary protection at an otherwise vulnerable period of time. The murine model has been the most widely studied regarding the processes of developing B cells. Although significant, such as the knowledge of developing B cell protein expression and the mechanism(s) involved in the generation of Ab diversity, these models have not accounted for the species-specific physiological mechanisms existing in birds, ruminants, rabbits, and other domestic animals, to generate mature B cells. Unlike mice, many species' enhance Ab diversity through an obligate period of gene modifications in gut-associated lymphoid tissues (GAL Ts). Outbred sheep were used to investigate the physiological events associated with GALT B cell development in ruminants. IPP B cells, as well as B cells from secondary lymphoid tissues, such as jejunal Peyer's patch (JPP), mesenteric lymph nodes (MLN), and prescapular lymph nodes (PSLN). A cellular tracking dye, 5, 6 Carboxyfluorescein Diacetate Succinimydl Ester (CFSE), a panel of monoclonal Abs (mAbs), as well as immuoohistochemistry (THC), were used to establish normal compositions of R cell subsets in fetal and neonatal animals. Additionally, we compared tissue-derived B cells and their response to specific mitogens while in culture. Specifically, we have documented the sequencing of cell surface protein expression by developing sheep B cells within the microenvironment of the IPP follicle. This sequencing intriguingly includes the expression of an ubiquitinated isoform of the CD2 l molecule after the expression of the normal CD21 molecule. We also have described the dual-role of the JPP as a primary lymphoid organ in sheep during the fetal stage of development and as a secondary site from parturition throughout life. Additionally, we observed an immunologically-latent period of suppressed B cell proliferation during the neonatal developmental stage of life. finally, we describe the successful utilization of a novel surgical technique used to administer CFSE in utero, a technique not previously documented. Data obtained from this experimentation has fortified our knowledge of ruminant lymphoid tissues and age-related events associated with B cell development. As a result of this study, we have a greater understanding of B cell development within the ruminant animal. This knowledge, as well as the results of future studies, will influence the ability to protect these vulnerable animals and may lead to novel therapeutic strategies to enhance neonatal immunity. This understanding of the developing immune system in young domestic animals is of extreme economic and environmental significance.

Library of Congress Subject Headings

B cells
Sheep -- Immunology
Ruminants -- Immunology
Immune system

Format

application/pdf

Number of Pages

85

Publisher

South Dakota State University

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