Elevated levels of interleukin-13 and IL-18 in patients with dengue hemorrhagic fever

Abstract

Interleukin (IL)-13 is produced by T helper 2 (Th2)-type cells and inhibits the production of proinflammatory cytokines by activated monocytes, while IL-18 is a pleiotropic cytokine that induces interferon-γ and plays an important role in the development of Th1-type cells. Role of the shift from a Th1-type response to Th2-type has been suggested in the pathogenesis of dengue hemorrhagic fever (DHF). This study was undertaken to investigate the possible protective/pathogenic role of IL-13 and IL-18 in patients with DHF. Sera were collected from a total of 84 patients with various grades of dengue illness and 21 normal healthy controls and tested for IL-13 and IL-18 levels using commercial enzyme-linked immunosorbent assay kits. The results showed that very low levels of IL-13 (4± 3 pg ml^-1) and IL-18 (15± 4 pg ml^-1) were detected in the sera of healthy controls. In dengue patients, the levels of IL-13 and IL-18 were the highest in the patients with DHF grade IV (205± 103 pg ml^-1 and 366± 155 pg ml^-1, respectively) and the lowest in patients with dengue fever (22± 12 pg ml^-1 and 76± 50 pg ml^-1, respectively). Both the cytokines appeared (IL-13=20± 11 pg ml^-1 and IL-18=70± 45 pg ml^-1) during the first 4 days of illness and reached peak levels (IL-13=204± 96 pg ml^-1 and IL-18=360± 148 pg ml^-1) by day 9 onwards. The presence of high levels of IL-13 and IL-18 during severe illness and late phases of the disease suggests that both of these cytokines may contribute to the shift from a Th1- to Th2-type response and thus to the pathogenesis of DHF.