Becs Hiltz | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Becs Hiltz. This seminar is open to the general public to attend.

PhD with Dr. Anne Laarman.

Zoom Link: https://ualberta-ca.zoom.us/j/98839591997

Thesis Topic: An Investigation of Colostral IgG in the Neonatal Bovine Intestine from Birth to “Gut Closure”.

Abstract: 

IgG absorption from colostrum is essential for transfer of passive immunity in the neonatal calf; despite best practices for colostrum feeding, some calves still have failure of transfer of passive immunity. Kinetics and mechanisms of IgG transport have not been investigated at the intestinal tissue level in the neonatal calf, and labeling methods for IgG have not enabled researchers to distinguish between colostrum derived IgG and experimentally supplemented IgG . A novel ELISA system was developed to distinguish between biotin-labeled IgG and non-labeled IgG if they are held in the same ratio. This ELISA system has the potential to be applied to proteins other than IgG. For animals, Holstein × Angus calves were assigned to one of 6 treatment groups, n = 6, 1) non-fed animals euthanized at 1hr of life, 2) non-fed animals euthanized at 24hrs of life, 3-6) animals fed colostrum at 1hr of life and euthanized at 6, 12, 18, or 24 hrs of life. Intestinal tissue samples from all calves were used in ex-vivo kinetic experiments to determine IgG transport rate and capacity, and additional samples were analyzed for histological features. IgG was measured in the luminal contents, intestinal tissue, via kinetic experiments, and colocalization to the IgG receptor, FcRn, was performed to analyze the passage and absorption of IgG in the neonatal calf from birth to 24hrs of life. Data showed that IgG absorption into serum reaches levels indicating transfer of passive immunity has been achieved by 12hrs of life in fed calves. IgG in the lumen of the intestine had high IgG concentrations at 6hrs of life (5hrs post feeding) but the concentrations dropped close to 0 by 12hrs of life (11hrs post feeding), showing that one feeding of colostrum passes through the intestinal tract, away from the absorptive types, by 12hrs of life. In the tissue itself, IgG concentration was highest in the proximal and distal jejunum and 6 and 12hrs of life, corresponding with increased serum IgG data. However, data showed that IgG transport capacity did not differ between birth and 24hrs of life with animals that were fed colostrum, a novel finding. Non-fed animals at 24hrs of life lost the capacity to transport IgG through the intestinal tissue, suggesting that age rapidly decreases absorptive capacity, and that feeding retains the absorptive capacity for IgG. In conjunction, 1hr and 24hr old non-fed animals exhibited IgG-negative vesicles in the intestinal villi, while 24hr old fed animals exhibited IgG-positive vesicles in the intestinal villi. The presence of empty intestinal vesicles did not correspond with intestinal transport of IgG, and thus IgG-negative vesicle number, thought to indicate transport capacity, does not have an effect on transport capacity. In the intestinal villi, IgG was colocalized to FcRn. FcRn was strongly colocalized to lymph vessels and weakly to blood vessels, showing that IgG is preferentially transported into the lymphatics instead of directly into serum, as has been previously suggested.