Semester of Graduation

Spring 2021

Degree

Master of Science (MS)

Department

Veterinary Clinical Sciences

Document Type

Thesis

Abstract

A more complete understanding of canine T-cell immunity is necessary for improving diagnostic and therapeutic approaches to canine diseases, developing cell-based canine immunotherapeutics, and evaluating dogs as large mammal models for comparative immunology research. Canine immunological studies are limited by the lack of established phenotypic markers identifying diverse differentiation states in canine T-cells. Differential expression of CD45RA (indicating antigen experience) and CD62L (indicating lymph node homing capability), shows promise as a tool to delineate canine naïve (TN), central memory (TCM), effector memory (TEM), and terminal effector memory (TEMRA) T-cells. The aim of this study was to characterize canine memory T-cell subsets and ultimately, validate use of CD45RA and CD62L for their identification.

By comparing T-cell subset proportions in dogs with inflammation and cancer to healthy dogs, we confirmed that, as in other species, subset proportions change with disease states in dogs. As expected, dogs with inflammation had decreased CD4+ TN proportions and increased CD8+ TEM proportions compared to healthy dogs. Furthermore, dogs with severe inflammation had increased proportions of CD4+ TN compared to those with milder signs. Possible explanations for this seemingly paradoxical finding that somewhat mirrors human studies include recruitment of TEM and TEMRA to inflamed tissues, dysregulated differentiation or accelerated TEMRA apoptosis, increases in circulating CD62L-expressing regulatory T-cells, and chronic drug effects.

Subset proportions in canine cancer patients were not significantly different compared to healthy dogs, most likely due to a majority of dogs harboring only localized disease. Emerging trends of decreased CD8+ TN and increased CD8+ TEMRA in subjects with systemic B-cell lymphoma suggest that subset differences may be present in more advanced cancer stages.

Finally, FACS-sorted canine CD8+ TN and TEMRA T-cells were evaluated for their proliferative capacity by assessing ConA-induced Ki-67 expression. Preliminary data suggest increased proliferative capacity in canine CD8+ TN compared to TEMRA T-cells, consistent with findings in humans and mice.

Taken together, these data provide additional evidence for the utility of CD45RA and CD62L in characterizing canine immune responses. Further optimization of functional assays on sorted canine T-cells and scRNA-seq are necessary to further define and functionally delineate canine T-cell memory subsets.

Committee Chair

Withers, Sita

Available for download on Monday, March 14, 2022

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