# Immune response in dogs with myxomatous mitral valve disease: insights into monocyte and lymphocyte subtypes and natural killer cells

## TL;DR

This study explores immune changes in dogs with heart disease, focusing on monocytes, T cells, and cytokines at different disease stages.

## Contribution

The study identifies immune cell and cytokine changes in dogs with MMVD at various disease stages, suggesting a role for inflammation.

## Key findings

- Monocyte percentages were higher in dogs with congestive heart failure compared to preclinical stages.
- Activated T helper lymphocytes were lower in compensated heart failure compared to other groups.
- Proinflammatory cytokine concentrations increased in advanced disease stages.

## Abstract

The immune response in dogs with myxomatous mitral valve disease (MMVD) is understudied.

Investigate the populations of monocyte subtypes, natural killer cells (NK cells), and T lymphocyte subtypes in dogs with MMVD and their relationships with selected cytokines and echocardiographic parameters at different stages of the disease and in comparison to healthy dogs.

Eighty-one client-owned dogs: 64 with MMVD (preclinical stage, compensated congestive heart failure [CHF], decompensated CHF) and 17 healthy dogs.

Cross-sectional study. Natural killer (NK) cells, monocyte subtypes, T lymphocyte subtypes, and B lymphocytes were identified using flow cytometry. Generalized linear models were used to compare variables between groups. Pairwise comparisons were performed using estimated marginal means with Tukey correction. P-value < .05 was considered significant.

The percentage of monocytes was higher in dogs with compensated and decompensated CHF compared with preclinical dogs. The percentage of activated T helper lymphocytes was lower in compensated CHF compared with all other groups. No differences in percentages were found for monocyte subtypes, NK cells, cytotoxic, regulatory and double positive T lymphocytes, or B lymphocytes. Concentration of monocyte chemoattractant protein-1 was higher in the decompensated CHF compared with all other groups, and the concentration of keratinocyte chemotactic-like chemokine was higher in the decompensated CHF compared with the preclinical group.

Higher concentrations and percentages of total monocytes and concentrations of proinflammatory cytokines in CHF suggest an inflammatory pathway in MMVD progression. Activated T helper lymphocytes may be downregulated in dogs with compensated CHF.