Examining Immune Receptor Signalling

Image flow cytometry showing goldfish neutrophils eating (phagocytosing) fluorescent 4.5µm beads.

Innate immunity is an essential component of the vertebrate antimicrobial defence system. One of these fundamental innate cell responses is phagocytosis, a process that involves dynamic remodelling of the plasma membrane during the capture and ingestion of extracellular material. While this mechanism is ubiquitous in the immune response of all multicellular animals, very little is currently known about this process in basal vertebrates.

​There are more than 25,000 known species of teleost (jawed) fish that thrive in diverse aquatic ecosystems populated with numerous bacterial, parasitic, and viral pathogens. Fish exhibit robust innate immune mechanisms that deal with this continuous assault including phagocytosis; but how these responses are specifically regulated in ectothermic vertebrates is largely unknown. Sequenced teleost genomes reveal a vast inventory of fish immune genes, including a large number and diversity of immune receptor-types. However, the functional roles played by these teleost receptor proteins remains to be determined. In an effort to understand conserved and divergent aspects of innate immune processes across vertebrates, our research focuses on the characterization of channel catfish (Ictalurus punctatus), goldfish (Carassius auratus), and zebrafish (Danio rerio) leukocyte immune-type receptors (LITRs). These efforts have recently uncovered new details regarding teleost immunoregulatory-mediated signaling pathways and their functional capabilities.

​Overall, we aim to understand the fundamental mechanisms controlling innate cellular defense responses in vertebrates. Our work has demonstrated LITRs as potent regulators of functional responses in different immune cell lineages using both conserved and unique intracellular signal transduction pathways. These findings establish LITRs as a new comparative model for studying the cellular control of innate immunity. As relatives of important mammalian immune receptor-types, studying LITRs has the potential to reveal novel details about highly conserved strategies for combating microbes across vertebrates. This work will produce mechanistic details regarding the fundamentals of immunoregulatory receptor-mediated control of phagocytosis and elucidate conserved molecular aspects connecting remodeling of the actin cytoskeleton with immunoregulatory receptor signaling.

Cell-Based Bioactivity Screening of Water Samples

A brightfield microscopy image of one of the cell lines (mouse macrophage RAW 264.7) we use to assess water immunotoxicity.

Our lab is also involved in examining how industrial, environmental, and municipally-sourced waters affect the health and function of cells. Currently, we focus on screening oil sands process affected waters (OSPW) and subsequent approaches to treating this effluent. These contaminated waters are generated from the bitumen mining processed in Northern Alberta and stored long-term in large tailing ponds that create potential for animal and human exposures due to ground seepage into the water table and/or leakage from the ponds. Therefore, in collaboration with Dr. Gamal El-Din (Dept. of Civil and Environmental Engineering, University of Alberta), our research uses mammalian macrophages as bioindicators of immunotoxicology (immune-based responses upon exposure to a substance), in addition to employing bacterial cytotoxicity screening of OSPW samples and associated approaches of remediation of it.
 
Beyond direct analytical measures and end-point toxicity tests, our bioindicator system provides a series of cell-based biological measures for monitoring and comparing water samples. These assays are used for determining the acute cytotoxicity of samples as well as sub-lethal assessments at the molecular, biochemical, and functional levels to provide informative readouts for detecting and tracking constituents of potential concern. Combined with the detailed analytical profiling of discrete test materials (e.g. water and tailings) provided by Dr. Gamal El-Din’s research, we are correlating sample composition profiles with specific sample-induced cellular responses. Overall, our cell-based bioindicator framework systems will be a valuable rapid, sensitive, and high throughput monitoring tool for sample analyses as well as cross-sample water quality comparisons when combined with abiotic profiles of constituents.
​

Header image: confocal microscopy of goldfish kidney tissue stained with fluorescent LITR antibodies. Photo credit: Samuel Amoah.