LYMPHOCYTE AND MACROPHAGE ACTIVATION IN BRONCHOALVEOLAR LAVAGE FLUID IN NOCTURNAL ASTHMA

Increased nocturnal airway narrowing is thought to occur as a conseque nce of an intensification of inflammatory processes at night. Lymphocy te and alveolar macrophage (AM) activation are thought to be associate d with the clinical expression of asthma, and may be important in the occurrence of nocturnal asthma as well. The expression of CD25 and HLA -DR receptors on lymphocytes from bronchoalveolar lavage (BAL) and per ipheral blood (PB) CD4(+), as well as of CD14, IgG Fc, and CD11/CD18 l eukocyte adhesion receptors on AM in BAL fluid and monocytes in PB, we re determined at 16.00 and 04.00 h by flow cytometry. Their relationsh ip with the occurrence of nocturnal asthma was investigated in eight n onatopic controls (Group 1) and 17 atopic asthmatic subjects, prospect ively assigned to groups with a mean circadian peak expiratory flow (P EF) variation < 15% (Group 2) and greater than or equal to 15% (Group 3). The occurrence of an increased circadian variation in PEF in asthm atic subjects was on the whole not associated with a day-night fluctua tion in lymphocyte numbers and subsets in PB or BAL fluid, nor with da y-night changes in receptor expression on AM from BAL or monocytes fro m PB. The only exception was the presence of a greater day-night chang e in the proportion of HLA-DR-expressing CD4(+) lymphocytes in the BAL fluid along with an increasing circadian PEF rhythm in asthmatic subj ects (r = 0.68, p = 0.03). A further finding was that a lower number o f BAL CD4(+) lymphocytes at daytime was significantly related to a hig her circadian PEF variation in asthmatic subjects (r = -0.66, p = 0.01 ). Additionally, asthmatics in Group 3 showed a greater expression of CD11b on AM from BAL fluid at 16.00 h (p = 0.05), and a significantly positive correlation was found for this parameter with the circadian v ariation in PEF of all asthmatic subjects (r = 0.72, p = 0.03). These findings show that increased nocturnal airway obstruction in asthma is not associated with an increased influx of lymphocytes and macrophage s into BAL fluid at night, nor with marked activation of these cells. Daytime presence of enhanced AM CD11b expression may predispose to the occurrence of nocturnal asthma.