(a) CXCR2 mRNA expression is markedly elevated during VILI. RT-PCR determination of CXCR2 mRNA in lung homogenates from mice placed on either high– or low–peak pressure/stretch ventilator protocol, or from normal nonventilated mice. Semiquantitative results are expressed as a ratio of each PCR product to β-actin band density (n = 4 mice per group). *P < 0.02. (b and c) FACS analysis of CXCR2. (b) Total number of leukocytes (CD45-positive cells) with cell surface expression of CXCR2 in whole-lung digest homogenates from mice placed on either high– or low–peak pressure/stretch ventilator protocol, or from normal nonventilated mice (n = 3 mice per group). *P < 0.02. (c) Total number of nonleukocytes (CD45-negative cells) with cell surface expression of CXCR2 in whole-lung digest homogenates from mice placed on either high– or low–peak pressure/stretch ventilator protocol, or from normal nonventilated mice (n = 3 mice per group). *P < 0.02.