Architecture and inflammatory cell composition of the feline lung with special consideration of eosinophil counts

An increase in the number of eosinophils in bronchoalveolar lavage fluid (BALF) is a hallmark of feline asthma; however, a wide range in the percentage of eosinophils in BALF has been documented in healthy cats. In this study, BALF and lung tissue were collected from 15 cats without respiratory disease, BALF was taken from 15 cats with asthma and lung tissue was collected from six different asthmatic cats. Total nucleated cell count (TNCC) and inflammatory cell percentages were measured in BALF and lung tissue was evaluated microscopically. Asthmatic cats had a significantly higher eosinophil count in lung tissue, but BALF TNCC did not differ significantly between groups. Cats without respiratory signs had significantly more numerous macrophages and lymphocytes in BALF than asthmatics, but significantly lower percentages of eosinophils (4.2 ± 7.8% versus 49.4 ± 20.6%, P <0.001). In healthy feline airways a BALF eosinophil percentage of <5% can be expected. Dominant microscopical findings in feline asthma include high eosinophil counts, airway remodelling and inflammation. There is good correlation between the findings in BALF and tissue in feline asthma.