Age-related variation in the cellular composition of equine bronchoalveolar lavage fluid.

This research investigates the variations in the cellular composition of bronchoalveolar lavage fluid (BALF) in horses as they age, from being a foal to the adult phase. The study employed a longitudinal analysis, examining changes in total nucleated cell count (TNCC) and percentages of specific cell types such as macrophages, lymphocytes, eosinophils, and more over time, which revealed significant differences in the cytologic profiles of BALF between foals and adult horses.

Methodology

• The research was conducted on horses at different stages of growth, specifically at one week, one month, two months, six months, and one year.
• Over this one-year period, BALF samples were serially collected for analysis from the same set of individuals to track changes as they progressed in age.
• The researchers used both the TNCC and protein concentration as assessment metrics, supplemented by cytology to identify the different cell types present in the BALF samples.

Results

• The study found that one-week-old and six-month-old foals had statistically higher TNCC than adult horses, without any significant alterations in total protein.
• One-month-old foals had the highest proportion of macrophages, much higher than those aged one year and adults.
• The counts of lymphocytes, an essential type of white blood cell, were notably lower in one-week and one-month-old foals, compared to yearlings and adults horses.
• The eosinophil percentage, another white blood cell type, was the least in foals aged one week to two months but peaked in six-month-old foals.
• Mast cells were most abundant in yearlings and adult horses, while the highest percentage of neutrophils was observed in foals of one week old.

Conclusions

• The results underscored marked differences in the cellular composition of BALF between foals and fully grown horses.
• Significant age-related changes were seen in TNCC and percentages of lymphocytes, macrophages, and eosinophils.
• This finding hints at the possible role of age and maturation in influencing pulmonary cellular components and potentially the overall immune response in horses.