Increased expression of the chemoattractant cytokines eotaxin, monocyte chemotactic protein-4, and interleukin-16 in induced sputum in asthmatic patients

Background: Induced sputum. from asthmatic patients has been recently used to assess inflammatory cells. We have previously reported an increased expr ession of Th-2-type cytokines in induced sputum of asthmatic patients. C-C chemokines, particularly eotaxin and monocyte chemotactic protein (,MCP)-4, are associated with eosinophilic infiltration. Interleukin (IL)-16 is asso ciated with chemotactic activity for CD4+ cells. Chemokine expression in BA L and bronchial biopsy specimens has been demonstrated in asthmatic airways , but not in induced sputum. Methods: We examined whether eotaxin, MCP-4, and IL-16 expression could be detected in induced sputum of asthmatic patients (n = 10), and whether the expression was increased compared to normal control subjects (n = 9). Eotax in, MCP-4, and IL-16 immunoreactivity were determined by immunocytochemistr y. In addition, inflammatory cells were investigated using markers for T ce lls (CD3), eosinophils (major basic protein [MBP]), macrophages (CD68), neu trophils (elastase), and epithelial cells (cytokeratin). Results: Our results showed that there was a significant difference in the percentages of MBP-positive and epithelial cells between asthmatic patients and normal control subjects (p < 0.05). However, there was no difference b etween these two groups in the percentage of CD3-, elastase-, and CD68-posi tive cells. Immunoreactivity for eotaxin, MCP-4, and IL-16 was expressed in the induced sputum of all asthmatic patients, and expression of these chem otactic cytokines was significantly greater than in control subjects (p < 0 .001, p < 0.005, and p < 0.001, respectively). Conclusions: This study showed that induced sputum could be used to detect chemokines in patients with bronchial asthma, and that the upregulation of chemotactic cytokines in the airways can be seen using noninvasive techniqu es.