Differential cell count and lymphocyte subsets in bronchoalveolar lavage during pneumonia with and without peripheral neutropenia

Abstract

One hundred immunocompromised HIV negative patients with microbiologically positive pneumonia underwent bronchoalveolar lavage (BAL) studies. Thirty cases showed peripheral neutropenia (< 1000 neutrophils/microL), 70 did not. The total cell number in BAL, the differential cell counts, and the lymphocyte subsets (CD4, CD8, CD19, CD57) were measured. Patients with pneumonia and normal or elevated peripheral neutrophils had a significantly increased total number of cells in BAL compared to patients with peripheral neutropenia (3.2 +/- 2 vs 1.3 +/- 0.6 x 10(5) cells/ml2 lavage fluid, p < 0.01). Ninety percent of the BAL differential cell counts obtained in patients exceeding 1000 neutrophils/microL showed a lymphocytic and/or neutrophilic alveolitis, whereas only 54% of patients with peripheral neutropenia displayed abnormal counts (p < 0.01). Yet the typical pattern of neutrophilic alveolitis was found more often for peripheral neutrophil counts over 1000/microL with high significance (p < 0.0001). Abnormal BAL cell patterns for neutropenic patients uniformly showed a lymphocytic alveolitis, only 10% additionally conformed with the pattern of neutrophilic alveolitis. Patients with pneumonia with and without peripheral neutropenia had similar findings in BAL lymphocyte subsets and exhibited a reduced CD4/CD8 ratio compared to controls (p < 0.05). The high susceptibility of severe neutropenic patients to pulmonary, especially fungal infections may be explained by the local lack of neutrophils.