An Investigation Into B Cells In Peripheral Blood And Gut Associated Lymphoid Tissues In The Red Eared Slider Turtle, Trachemys Scripta

As in endotherms, immunity in ectotherms is vital to survival and contributes to the overall fitness of an organism. For reptilians, there are a number of environmental factors, such as temperature, season, and pathogen prevalence, which are known to influence both innate and adaptive immunity. Of particular interest, is the effect of these factors on B cells, a component of adaptive immunity. Reptilian B cells are reported to secrete antibodies, much like their mammalian counterparts, and undergo phagocytosis. The work reported here primarily focused on understanding the effect of environmental temperature, incubation temperature, and nesting season on B cells in the model reptile the red eared slider turtle (Trachemys scripta). First, we investigated the effect of environmental temperature on the functions of peripheral blood B cells isolated from adult red eared sliders. Specifically, we examined B cell phagocytosis and the number of antibody secreting cells at four biologically relevant temperatures, 20°, 25°, 30°, and 35°C. Normal activity range of red eared sliders is reported between 25°-30°C, therefore we hoped to elucidate the effect of temperature on B cell functions above and below this range. We found that the ability of B cells to phagocytose was not affected by temperature. Additionally, we report that the number of antibody cells was significantly affected by temperature with increased and decreased antibody secretion between 20°-25°C and 30°-35°C, respectively. Our secondary focus was to characterize B cells in the gut associated lymphoid tissues (GALT) of red eared slider hatchlings. In our study population, turtles lay two clutches during the summer, an early clutch and a late clutch. We aimed to examine the effect of incubation temperature and early vs. late season on B cell distribution in the small intestine of hatchlings derived from the 2014 and 2015 nesting season. To test the effect of incubation temperature, eggs were incubated in fluctuating temperature treatments with mean temperature of 26.5°C (low), 27.1°C (medium), or 27.7°C (high). We found that incubation temperature significantly affected the number of B cells in early season clutches. Specifically, clutches from the low temperature treatment had more B cells than clutches from the higher incubation temperature treatments. Additionally, preliminary data suggested that B cell presence in the small intestine may be significantly affected by nesting season with a large proportion of late season hatchlings exhibiting no B cells. We also examined maternal antibody allocation to early and late season eggs. Maternal antibody levels in yolk were not affected by nesting season; however, they were significantly affected by clutch identity. Overall, the work presented here explores the importance of B cells in reptilian immunity