Date of Award

2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Cell & Molecular Biology

First Advisor

Gudrun F. Debes

Abstract

The trafficking of innate-like lymphocytes, such as γδ T cells and B-1 B cells, has garnered comparatively little attention from the immunological community relative to conventional T and B cells. However, recent studies have shown that innate-like cell subsets are critical for immune regulation and host defense. In this study, we use a classic ovine lymph cannulation model to describe the phenotype and function of γδ T cells migrating through the skin. We find that γδ T cells traveling in the skin-draining afferent lymph are IFN-γ- and/or IL-17-producing effector cells that express high levels of the skin- and inflammation-seeking molecule E-selectin ligand. Notably, they also lack expression of CCR7, indicating that they use alternative receptors for egress. Next, we analyze B cell subset composition, repertoire, and trafficking in the skin of sheep in the lymphatic cannulation model. We find a heterogeneous population of B cells in the skin and skin-draining lymph increases in inflammation that contains a subset of B-1-like B cells coexpressing IgM and CD11b. Furthermore, we show that skin accumulation of B cells and antibody-secreting cells during inflammation increases local antibody titers, which may augment host defense and autoimmunity. We then extend our findings of cutaneous B-1 B cells to the mouse, analyzing both uninflamed skin and skin with chronic inflammation from complete Freund's adjuvant, well as human tissue. We find that B-1 B cells, unlike conventional follicular B-2 B cells, efficiently enter into the inflamed skin and differentially express the trafficking molecule α4β1 integrin (VLA-4), which facilitates their entry. Furthermore, innate B cells are a contributing source of cutaneous IL-10 in both IL-10-reporter mice and normal human skin.

These findings, initiated in the sheep model then followed up and supported by experiments in mice and human tissues, demonstrate the evolutionary similarity between mammalian species. They also validate the utilization of multiple models to allow for experimental setups not possible in all species. More importantly, the further characterization of γδ T cells and the new description of skin B and B-1 cells uncovers additional targets for regulating the cellular composition of a cutaneous immune response. In summary, the data support a model in which innate-like lymphocytes are poised to migrate into barrier sites, including the skin, where they rapidly provide requisite effector functions, such as cytokine and/or antibody production, and fulfill an emerging role in skin immunity.

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