Date of Award:

12-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Committee Chair(s)

Susannah S. French

Committee

Susannah S. French

Committee

Alan H. Savitzky

Committee

Heloisa Rutigliano

Committee

Stesha Pasachnik

Committee

Sara Freeman

Abstract

The immune system is important to an animal’s survival against disease-causing agents and physical injuries. Accordingly, many resources are required to maintain and activate the immune system (such as energy). However, as these resources also need to be shared with other important systems of the body, the portion of resources that can be allotted to the immune system is variable. Thus, many different factors may alter how well the immune system operates. My dissertation sought to understand what sorts of factors can lead to changes in the immune system. Reptiles are known to have a very robust immune system. Therefore, we used iguanas to test what kinds of variables can affect the immune system. Dietary changes can affect the immune system, especially if the diet does not match what the organism has evolved to eat. Changing the diet of an organism can also change the gut microbiome (microbes colonize the intestines of most vertebrates and those microbes can influence physiology) of the organism. The gut microbiome in turn can also affect the immune system as the micro-organisms living in the gut create products that can communicate with immune cells and components. My 2nd and 3rd chapters study how immune function changes when diet and the gut microbiome change. I found that a high sugar diet results in an altered gut microbiome and an overactive immune system but when faced with a challenge, immune response was lacking (suppression). When the gut microbiome was changed using antibiotics to kill those microbial communities, immune function, surprisingly, improved. This suggests that while changes to the gut microbiome also change immune function, it is not always in a detrimental way. Finally, in my 4th chapter, I studied how parasites, injuries (such as tail break), and presence of different human disturbances, affects the immune system in an endangered iguana, C. oedirhina, in the wild. I found that these reptiles have a resilient immune system that was not affected by any of these factors, further supporting the idea that reptiles generally have a strong immune system.

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