Expression of RANTES mRNA and protein in airways of patients with mild asthma

Chemoattractant cytokines (chemokines) such as RANTES, are potent chemoattractants for eosinophils, T lymphocytes, and monocyte/macrophages. We examined RANTES mRNA and protein expression in bronchial biopsies and bronchoalveolar lavage (BAL) cells from patients with mild asthma on β₂- adrenergic agonist therapy only. Using quantitative polymerase chain reaction (PCR), mean RANTES starting cDNA was 110 ± 18 fg/pg β-actin in asthmatics compared with 33.7 ± 11.0 fg/pg in normals (p < 0.003) but there was no significant difference in RANTES mRNA expression in BAL cells between the two groups. Immunohistochemical staining of cryostat sections of bronchial biopsies with an anti-RANTES antibody using peroxidase antiperoxidase method revealed constitutive staining in airway epithelial cells, airway smooth muscle, and subepithelial cells. However, there was no difference in the number of RANTES-staining cells between normal subjects and asthmatics despite significantly increased numbers of CD4⁺ T-cells, CD68⁺ macrophages, and MBP⁺ eosinophils in mucosal biopsies obtained from asthmatics. Double-staining revealed expression of RANTES in a proportion of CD3⁺ T lymphocytes. Thus, RANTES is constitutively expressed in the airways and RANTES mRNA is elevated in airways of patients with mild asthma, supporting a role for RANTES in normal and asthmatic airways.