Abstract
Background:
Breed-specific differences in humoral and cellular immune parameters have been reported in different species. The Pygmy and Ardi goat populations are two local breeds in Saudi Arabia.

Aim:
The aim of the present study was to compare the distribution of lymphocyte subsets in the blood of goats of the Ardi and Pygmy breeds.

Methods:
Monoclonal antibodies against lymphocyte cell surface markers were used in combination with flow cytometry to determine the percentages and absolute numbers of lymphocyte subsets in blood samples collected from the two Saudi Arabian local breeds.

Results:
The results of the present study show an overall dominance of goat CD4+ T helper cells within blood lymphocytes, followed by comparable percentages of CD8+ cytotoxic T cells, BAQ44A+ B cells, and γδ T cells, and a less frequent fraction of NKp46+ NK cells. This indicates lymphocyte subset frequencies that are in agreement with previous reports on the lymphocyte composition in goat blood. The comparison of lymphocyte composition among the goat breeds identified higher percentages as well as absolute numbers of both helper and cytotoxic T cells in Pygmy than in Ardi goats. In contrast, the abundance of γδΤ cells was higher in Ardi vs. Pygmy goats.

Conclusion:
The different percentages and absolute numbers of helper and cytotoxic T cells indicate different immune responsiveness of the two goat breeds to extracellular and intracellular pathogens, respectively. The clinical significance of these findings will be investigated in future studies focusing on the comparative immune responses of the two breeds to experimental infections with distinct intracellular and extracellular pathogens.

Key words: Pygmy goats, Ardi goats, Breed, Flow cytometry, Lymphocyte subsets