Immunophenotyping of canine bronchoalveolar and peripheral blood lymphocytes

The immunophenotype of canine lymphocytes obtained by bronchoalveolar lavage (BAL) was investigated and compared with that of peripheral blood leukocytes (PBL). Indirect immunofluorescence, generated by monoclonal antibodies (mAb) specific for canine CD5, CD4, CD8, CD45pan, CD45RA, MHCII and THY-1, was detected by flow cytometry. In comparison with PBL, in BAL there are fewer lymphocytes positive for CD45RA (75.4 ± 12.6% vs. 42.3 ± 9.4%; P < 0.05) and MHCI I (97.0 ± 2.9% vs. 74.0 ± 7.6%; P < 0.01), while there are more cells positive for CD8 (19.0 ± 3.6% vs. 29.5 ± 12.0%; P < 0.05). Thus there is a lower CD4CD8 ratio in the cell compartment accessible by BAL (2.2 ± 0.3 vs. 1.3 ± 0.6; P < 0.005). The immunophenotype may be stable over time, as indicated by reexamination of cells obtained from one dog at four times over 1 year. Investigating the phenotype of lymphocytes from three different locations of the right lung, the cranial lobe lymphocytes show a lower CD4CD8 ratio in comparison with PBL (1.81 ± 0.35 vs. 1.12 ± 0.31, n = 5; P < 0.02). In general, less MHCII positive lymphocytes (P < 0.001) and greater immunophenotype variability of results were found in these separate samples compared with pooled samples from these locations.