Date Thesis Awarded

5-2017

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Patty Zwollo

Committee Member

Lizabeth Allison

Committee Member

Drew Lamar

Committee Member

Tom Marshall

Abstract

Rainbow trout are heavily affected by Flavobacterium psychrophilum, a bacterium which is highly contagious in cold water. This bacterium causes Bacterial Cold Water Disease (BCWD) in the fish, which leads to severe symptoms and often results in death. This bacterium’s contagion poses a problem for trout hatcheries, which harvest over 1,000,000 lbs of these fish a year. The National Center for Cool and Cold Water Aquaculture has bred two distinct lines of rainbow trout: one line that is heavily susceptible to F. psychrophilum, and one that is resistant to it. Although this lab was able to genetically select the lines, the mechanisms which allow for resistance to F. psychrophilum is still unknown. We are using these two lines of fish to study differences in immune cell patterns between the lines.

This study focuses on IgM and IgT expressing (or secreting) B cells. Fish from each line were challenged with either phosphate buffer saline (PBS) or live F. psychrophilum. Using flow cytometric analysis and qPCR, B cell abundances were compared between lines and treatments. This study found that challenged susceptible fish show significantly less IgT+ B cells than resistant fish through flow cytometric analysis. Similarly, susceptible fish had significantly less tau immunoglobulin secreting cells than mock susceptible fish, mock resistant fish, and challenged susceptible fish. Additionally, significant negative correlations were seen between IgM+ or IgT+ B cells and pathogen load. Other significant negative correlations were observed between IgM or IgT secreting cells and pathogen load. These results lead us to believe that the IgT isotype is protective for rainbow trout, particularly in regards to this bacterium.