Background: Induced sputum from asthmatic patients has
been recently used to assess inflammatory cells. We have previously
reported an increased expression 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 associated with
chemotactic activity for CD4+ cells. Chemokine expression in BAL 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).
Eotaxin, MCP-4, and IL-16 immunoreactivity were determined by
immunocytochemistry. In addition, inflammatory cells were investigated
using markers for T cells (CD3), eosinophils (major basic protein[
MBP]), macrophages (CD68), neutrophils (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
between these two groups in the percentage of CD3-, elastase-, and
CD68-positive cells. Immunoreactivity for eotaxin, MCP-4, and IL-16 was
expressed in the induced sputum of all asthmatic patients, and
expression of these chemotactic cytokines was significantly greater
than in control subjects (p < 0.001, p < 0.005, and p < 0.001,
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 techniques.