Date of Graduation

8-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor

Gisela F. Erf

Committee Member

Nicholas Anthony

Second Committee Member

Hilary D. Chapman

Third Committee Member

Charles Rosenkrans

Abstract

Pattern recognition receptors (PRRs) on host cells recognize motifs known as pathogen associated molecular patterns (PAMPs) that are common to groups of microbes. Examples include LPS on Gram-negative bacteria, the structural motif PGN common to all bacteria, MDP the smallest immunostimulatory unit of PGN, and poly I:C the dsRNA analog. PAMP recognition by and stimulation of the innate immune system is crucial to an individual’s ability to quickly limit microbial growth and stimulate the adaptive immune system. Characterization of the in vivo immune responses initiated by PAMPs has not been directly addressed. Using growing feathers (GF) as a novel intradermal test site along with concurrent blood sampling, we examined the time-course, phenotype, and severity of PAMP (LPS, PGN, MDP, or poly I:C) -elicited leukocyte and cytokine responses in both the peripheral blood circulation (automated hematology analysis) and at the local injection-site (pulp of GF; immunofluorescent staining of pulp cell suspensions). Intradermal injection of LPS or PGN in the pulp of GF resulted in increased heterophil levels in the blood and local tissue as well as smaller increases in macrophage proportions in the tissue. However, injection of PGN also resulted in the rapid recruitment and sustained presence of high levels of T and B lymphocytes at the local tissue site. Unlike PGN, its derivative MDP was not found to be highly immunostimulatory. Poly I:C injection also initiated a unique leukocyte infiltration profile with rapid (4-8 h) increases in macrophages and B cell levels in the pulp of injected GF. Injection of PAMPs (except MDP) in GF was shown to stimulate mRNA expression of IL-1, IL-6, IL-10, and CXCL8, and at lower expression levels IL-4 and IFN. As the first comprehensive investigation into the immunostimulatory effects of PAMPs in a complex tissue, we show that intradermal administration of PAMPs initiates an elaborate cascade of responses not seen in single cell in vitro studies. Future studies building upon the research reported here will continue to evaluate and dissect innate immune responses in poultry and will find direct application in the development of immunomodulatory treatments, vaccine adjuvants, and breeding/management strategies to improve poultry health.

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