ACTIVATION OF NEUTROPHILS WITHIN PULMONARY MICROVESSELS OF RABBITS EXPOSED TO CIGARETTE-SMOKE

Previous studies have shown that polymorphonuclear leukocytes (PMN) are delayed in the pulmonary capillaries by the presence of cigarette smoke. To determine if the PMN delayed by smoking are activated, we estimated the in vivo expression of CD11/CD18 and L-selectin on the surface of PMN in lungs and peripheral blood of rabbits because these molecules are known to be upregulated and downregulated, respectively, on the surface of activated PMN. New Zealand white rabbits (3.5 +/- 0.1 kg) were exposed to either air (n = 5) or cigarette smoke (n = 5), and we used an established protocol to measure pulmonary vascular blood flow, volume, and red blood cell (RBC) transit time in the left lung. The right lungs were then fixed in 0.025 % glutaraldehyde and stored in liquid nitrogen. Ultrathin sections were immunolabeled with either the anti-CD18 monoclonal antibody 60.3 or the anti-L-selectin antibody Dreg-200, followed by a secondary antibody conjugated to 10 nm colloidal gold. The target antigens were quantified by counting the number of gold particles per micron (G/mum) of PMN surface membrane. The data show that smoke exposure had no effect on pulmonary blood flow, volume, or RBC transit time. However, it increased the expression of CD11/CD18 on intravascular PMN in the upper region of the lung (control, 7.4 +/- 1.3 G/mum; smoke-exposed, 13.2 +/- 3.3 G/mum; P < 0.05) and decreased the expression of L-selectin on intravascular PMN in both the lower (control, 5.5 +/- 2.0 G/mum; smoke-exposed, 2.6 +/- 1.5 G/mum; P = 0.05) and the upper (control, 6.8 +/- 1.4 G/mum; smoke-exposed, 2.6 +/- 1.2 G/mum; P < 0.05) regions. Smoke exposure did not significantly change the expression of the two adhesion molecules on circulating PMN. We conclude that the presence of cigarette smoke in the alveoli activates PMN in the microvessels of the lung.