Analysis of bronchoalveolar lavage from human lung transplant recipients by flow cytometry

Bronchoalveolar lavage (BAL) cells and peripheral blood leucocytes (PBL) from 24 lung transplant recipients were analysed for leucocyte subsets and expression of cell surface antigens. Total and differential white cell counts were performed on BAL, and lymphocyte subsets were evaluated in both BAL and peripheral blood. Measurement of immunofluorescence by flow cytometry was used to assess the percentage of: T cells (CD3+); T-helper cells (CD4+); T-cytotoxic/suppressor cells (CD8+); and activated lymphocytes (HLA-DR+). Lymphocyte subsets in BAL demonstrated marked differences to those in blood. A lower percentage of CD3+ and CD4+ lymphocytes were found in BAL, whereas CD8+ cells were more prevalent in BAL than in PBL. The mean CD4:CD8 ratio was significantly lower in BAL (1:1) than in blood (2.1:1). In the absence of pulmonary infection, there was a trend for a lower CD4:CD8 ratio in BAL associated with acute rejection (1.1:1) and obliterative bronchiolitis (1:1), when compared to the group with no evidence of rejection (1.4:1). In the absence of pulmonary rejection, pulmonary infection was associated with a marginally lower CD4:CD8 ratio in BAL (0.7:1), than when infection was absent (1.4:1). This difference was more evident in cases of cytomegalovirus (CMV) infection with a mean CD4:CD8 ratio of 0.3:1, compared to 1.5:1 in the absence of CMV disease (P < 0.05).