Phenotypic analysis of bronchoalveolar lavage fluid lymphocytes in horses with chronic pulmonary disease.

A panel of specific antibodies against CD3, CD4, CD5, CD8, MHC I and II was used in single and two colour flow cytometry to define T cell subpopulations in bronchoalveolar lavage fluid of horses affected with chronic obstructive pulmonary disease and of healthy controls. According to the results of the clinical examination including bronchoscopy and cytology of the tracheal aspirate the horses were divided into four groups (healthy, subclinically to mildly affected; moderately affected, and severely affected). All groups of horses had a similar percentage of CD3+ cells in the BALF. Compared to controls, severely affected horses had a significantly increased number of CD4+ cells in the BALF, but a similar percentage of CD4+ cells whereas mildly and moderately affected horses had a decreased percentage. The percentage and number of CD8+ cells and the percentage of CD8+/MHCII+ cells in the BALF was found to be higher than normal and varied according to the disease state. This novel finding raises the possibility that not only the CD4+ cells but also the CD8+ cells are involved in the pathogenesis of COPD. The percentage and the number of CD8+ cells in BALF might be of diagnostic value to detect subclinical to mild cases of COPD.