Increased interleukin-13 expression in patients with sarcoidosis

Area of Science:

• Immunology
• Respiratory Medicine

Background:

• Sarcoidosis is a systemic granulomatous disease of unknown etiology.
• Inflammation in sarcoidosis involves Th1 cytokines like tumor necrosis factor alpha (TNFalpha).
• Interleukin 13 (IL-13), a Th2 cytokine, can suppress TNFalpha in monocytes.

Purpose of the Study:

• To investigate the role of IL-13 as a potential anti-inflammatory cytokine in sarcoidosis.
• To assess IL-13 expression in patients with sarcoidosis compared to healthy controls.

Main Methods:

• RT-PCR was used to measure mRNA expression of IL-13, IL-4, IL-10, and TNFalpha in bronchoalveolar lavage (BAL) cells and peripheral blood mononuclear cells (PBM).
• IL-13 protein levels were quantified in BAL cell culture supernatants.
• Immunocytochemistry was performed to localize IL-13 protein in BAL cells.
• TNFalpha concentrations were measured with and without stimulation by recombinant human (rh) IL-13, rhIL-10, and lipopolysaccharide (LPS).

Main Results:

• IL-13 mRNA expression was significantly elevated in BAL cells and PBM of sarcoidosis patients compared to controls.
• TNFalpha mRNA expression was significantly higher in BAL cells of patients.
• IL-13 protein was detected in alveolar macrophages of patients and led to decreased TNFalpha concentrations.
• No significant differences in IL-4 or IL-10 mRNA expression were observed between groups.

Conclusions:

• IL-13 expression and secretion are increased in BAL cells and PBM in sarcoidosis.
• Alveolar macrophages are a potential source of IL-13 in sarcoidosis.
• IL-13 exhibits an anti-inflammatory effect by modulating TNFalpha in sarcoidosis.