The canine T cell receptor repertoire.

Background: Tseek is a method of sequencing T cell receptor (TCR) repertoires with minimal bias. This work aimed to develop methods to characterize the TCR repertoire in dogs, identify influences such as genetic lineage and age, and evaluate the use of repertoires to monitor immune status in dogs.

Methods: Two studies were conducted to develop the techniques and characterize the effect of individual, breed, and age. One study analyzed RNA data from individuals (n = 32), 8 from each of 4 breeds, sampled at 2 time points a year apart. The second, lifestage study, used individuals within a single breed (Labrador Retriever) with ages dispersed across a broad range (0.2 to 12 yr, n = 50). Tseek was used to process samples for sequencing, to identify the V, and J segments to annotate the CDR3, which were then analyzed to draw inferences.

Results: The TCR repertoires had signatures of breeds, and of the individual, with stability over at least a year. Across the lifestage study, littermate-specific characteristics were not detected, but an age-related effect was observed: older dogs exhibited reduced diversity characterized by a greater abundance of individual-specific high-frequency clones, while puppies had a more diverse repertoire.

Conclusion: An individual's TCR repertoire includes stable information, indicative of the individual, breed, and age-related decline. The α and β chain repertoires had distinct properties in the breed-specific signatures, indicating differential influences on their selection, despite their pairing in each T cell. Consistent, age-related changes can be seen in the repertoire, but their impact on immune system needs to be delineated.