Different distributions of lung and blood lymphocyte subsets in pediatric AIDS or tuberculosis

Pulmonary immunity has not been studied in children with acquired immunodeficiency syndrome (AIDS) or tuberculosis (TB), even though lungs of both children and adults infected with human immunodeficiency virus (HIV-1) or Mycobacterium tuberculosis are affected frequently and severely. In the present studies, the distributions of T (CD3+, CD4+, CD8+) and B (CD19+) lymphocytes in bronchoalveolar lavage fluid (BALF) and blood of children with AIDS (N = 28) and children with pulmonary TB (N = 18) were determined using direct immunofluorescence (flow microfluorimetry). The distributions of lymphocyte subsets in BALF differed dramatically from those in blood. In pediatric AIDS, reduction of CD4/CD8 ratio was much more pronounced in BALF than in peripheral blood (0.15 +/- 0.04 vs. 0.43 +/- 0.11). This difference was due to selective depletion of BALF CD4+ lymphocytes, rather than to a great influx of CD8+ cells into the lung. In childhood TB, the CD4/CD8 ratio in BALF also was significantly decreased, despite its elevation in blood (1.02 +/- 0.26 vs. 1.96 +/- 0.32). The results show that (1) examination of peripheral blood lymphocytes does not reflect the kind and extent of changes observed in the distribution of pulmonary lymphocyte subsets, and (2) the profound decrease of the CD4/CD8 ratios in BALF of children with AIDS or TB is due to decreased percentages and absolute numbers of BALF CD4+ lymphocytes. The data suggest that analysis of BALF provides a more accurate evaluation of the patient pulmonary immune status than monitoring peripheral blood.