# Hematological Changes and Immunomodulation of Neutrophil and Monocyte Populations in Shelter Dogs

## TL;DR

This study shows that chronic stress in shelter dogs alters immune cell function, offering a new way to assess animal welfare.

## Contribution

The study introduces immune system monitoring as a novel method to evaluate stress effects in shelter dogs.

## Key findings

- Stress in shelters alters surface receptors on neutrophils and monocytes.
- Leukocyte apoptosis rates increase under chronic stress conditions.
- Duration of shelter stay influences immunomodulation and adaptation mechanisms.

## Abstract

Animal welfare plays a pivotal role in health assessment in veterinary medicine. Dogs living in shelters often face long-term stress, which can significantly impact their well-being. Commonly used psychological evaluations and checking cortisol levels provide useful insights but may not fully reflect how stress affects immune system functions. In this study, we investigated hematological and biochemical parameters, as well as potential immunomodulation in different living schedules of dogs kept in shelters. We focused on blood cell count and quality changes and also assessed the level of surface antigen expression (TLR4 and MHCII) on neutrophils and monocytes. Moreover, we measured how many of these cells were prone to cell damage and death. The aim of our study was to determine whether the immune system remains efficient under chronic stress conditions. Our findings revealed that stress in the shelter environment modulates immune responses by altering cellular adaptation mechanisms in order to maintain homeostasis. This study provides a novel perspective by highlighting immune system monitoring as a valuable addition to the assessment of animal welfare.

Environmental impact plays a pivotal role in forming the welfare of shelter dogs exposed to chronic stress. Standard methods of animal health monitoring, such as psychological evaluation or cortisol measurements, do not fully reflect modulation of the immune system. Functional cellular changes may be subtle and observed only at the molecular level. Therefore, the aim of this study was to characterize the immune function of shelter dogs kept on different timetables in comparison with client-owned dogs. We focused on potential alterations of antigen processing by neutrophils and monocytes in animals undergoing different durations of stress. Hematological and biochemical parameters were evaluated, and changes in TLR4 and MHC Class II expression on neutrophils and monocytes isolated from peripheral blood were determined. Additionally, we measured the percentage of apoptotic cells within these leukocyte populations. Our study revealed that stressful conditions can alter the molecular pattern of surface receptors on neutrophils and monocytes, as well as the leukocytes apoptosis rate. The obtained data also indicated that the dogs’ duration of stay in the shelter plays an important role in immunomodulation and triggering their adaptation mechanisms. These results bring a new perspective and will be crucial in developing improved guidelines for monitoring and promoting the welfare of shelter dogs.