Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Microbiology and Preventive Medicine

First Advisor

Judith R. Stabel

Second Advisor

Michael J. Wannemuehler


The purpose of this work was to investigate the interaction of the pro-inflammatory cytokine, IFN-gamma, and the anti-inflammatory cytokines, TGF-beta and IL-10, in the subclinical and clinical stages of Johne's disease. A retrospective quantitative analysis of IFN-gamma, IL-10 and TGF-beta mRNA gene expression in tissues such as ileum, ileal-cecal junction, ileal-cecal node, and mesenteric lymph node obtained from cows naturally infected with Mycobacterium paratuberculosis and healthy non-infected control cows revealed an upregulation of IL-10 and TGF-beta in tissues obtained from clinically infected animals but not in tissues obtained from healthy or subclinically infected cows. Analysis of IFN-gamma mRNA gene expression in these tissues showed that expression of this cytokine is upregulated only in subclinical cows. We further evaluated the effects of exogenous IFN-gamma, IL-10 and TGF-beta in an extended culture system (7--12 days) using unfractionated PBMC cultures from naturally infected and healthy non-infected cows after infection with live M. paratuberculosis. We determined that the presence of IL-10 and TGF-beta in culture supernatants was correlated with decreased ability of monocyte-derived macrophages in the unfractionated cell cultures to kill M. paratuberculosis in vitro, with a resultant decrease in IFN-gamma production in these cultures. IL-10 and TGF-beta were upregulated in response to in vitro infection in cell cultures from infected animals regardless of their disease status. Prior to in vitro infection with M. paratuberculosis TGF-beta levels were lower in subclinically infected animals compared to clinically infected or healthy animals. After in vitro infection, TGF-beta levels in culture supernatants of subclinically infected animals were similar to that of healthy animals. This is the first study to investigate the interactive roles of IFN-gamma, IL-10 and TGF-beta in natural and experimental M. paratuberculosis infections. The data presented here suggest an important regulatory role of anti-inflammatory cytokines IL-10 and TGF-beta on IFN-gamma production and the ability of macrophages to kill M. paratuberculosis in vitro.



Digital Repository @ Iowa State University,

Copyright Owner

Mohammad Subhi Khalifeh



Proquest ID


File Format


File Size

121 pages