We generated interleukin-5 receptor alpha chain (IL-5R alpha)-deficient (IL-5R alpha-/-) mice by gene targeting. The IL-5R alpha-/- mice showed decreased numbers of B-1 cells concomitant with low serum concentrations of IgM and IgG3. They showed no IL-5-induced enhancement of B cell responses to T-independent antigens. The number of alpha beta T cell receptor-positive thymocytes tended to decrease in 3-week-old IL-5R alpha-/- mice, returning to normal by 6 weeks of age. The IL-5R alpha-/- mice produced basal levels of eosinophils, while their bone marrow cells failed to form eosinophilic colonies in response to IL-5. Impaired eosinophilopoiesis in IL-5R alpha-/-mice enhanced the survival of Angiostrongylus cantonensis. These results indicate that IL-5-induced eosinophils serve as potent effector cells in the killing of Angiostrongylus cantonensis in mice.

Summary MUC2 mucin is a secretory glycoprotein which is produced from the intestinal goblet cells and is a major component of the intestinal epithelial mucus. The biological function of MUC2 mucin is considered to be the protection of intestinal epithelial surface, whereas the regulatory mechanism of MUC2 mucin production in immune response is not completely understood. We have studied the effects of cytokines, IL-4, IL-13 and TNF-α , on the regulation of MUC2 mRNA in the human colonic cancer cell lines, LS174T and HT29. The quantitative reverse transcription-polymerase chain reaction showed that single addition of IL-4, IL-13 and TNF-α to cell culture induced about two-fold increase of MUC2 mRNA level in LS174T cells. Interleukin-4 and IL-13 activated phosphorylation of mitogen-activated protein kinase in LS174T cells. A specific inhibitor of mitogen-activated protein kinase pathway, U0126, totally inhibited the increase of MUC2 mRNA by IL-4 or IL-13 in those cells. Therefore, mitogen-activated protein activation of kinase is required for the increase of MUC2 mRNA by IL-4 or IL-13 in LS174T cells. In contrast to LS174T cells, only TNF-α increased MUC2 mRNA through a mitogenactivated protein kinase pathway in HT29 cells that express low levels of MUC2 mRNA. These findings sustain a novel phenomenon that MUC2 mRNA expression is differently controlled by IL-4, IL-13, or TNF-α in LS174T and HT29 cells, whereas the mitogen-activated protein kinase pathway plays a role in the MUC2 mRNA expression induced by those cytokines in both cell lines.

Effects of depressed eosinophilia on the development of Angiostrongylus cantonensis in the mouse were studied using monoclonal rat anti-mouse-interleukin-5 antibody (anti-IL-5). The administration of anti-IL-5 strongly depressed peripheral, cerebrospinal fluid (CSF) and medullary eosinophilic responses in mice infected with A. cantonensis, when compared with groups treated with phosphate-buffered saline solution (PBS) alone or isotype-matched rat IgG. There was no significant difference in A. cantonensis antigen specific IgG and IgE antibody responses between rat IgG treated and anti-IL-5 treated mice. Intracranial worm recovery in anti-IL-5 treated mice was consistently high throughout the course of the study and some worms migrated from the brain to the lungs. By contrast, almost all the intracranial worms in the mouse groups treated with PBS alone or rat IgG died before day 32. These data clearly indicate that IL-5 is essential for eosinophil responses in A. cantonensis infected mice and also that eosinophils serve as a potential effector cell in the killing of the intracranial worms in mice.

For determination of the kinetics of cytokine production and its possible role in host resistance to Angiostrongylus cantonensis in the mouse, Th1 [interleukin 2 (IL-2) and interferon gamma (IFN-gamma] and Th2 (IL-5 and IL-4) cytokine production in the cerebrospinal fluid (CSF), sera, and culture supernatants of spleen cells (SC) or cervical lymph-node cells (CLNC) of infected BALB/c and C57BL/6 mice was assessed by a sandwich enzyme-linked immunosorbent assay (ELISA). IL-5 and IL-4 were detected in CSF of both strains, with a peak response occurring at around days 12-15 and 20 postinfection (p.i.), respectively. A reverse transcriptase-polymerase chain reaction (RT-PCR) assay also revealed prominent IL-5 and IL-4 mRNA expression in T-cells but not in eosinophils in CSF. SC and CLNC stimulated with A. cantonensis young adult-worm antigen released IL-5 in vitro at and after day 20 p.i. Contrarily, IFN-gamma production in CSF and SC or CLNC culture supernatants was almost negligible before day 30 p.i. IL-5, IL-4, and IL-2 production in culture supernatants was rather prominent in resistant C57BL/6 mice as opposed to susceptible BALB/c mice as assessed by the magnitude of increase over preinfection levels. Antigen-specific IgG1 (but not IgG2a) responses were more prominent in C57BL/6 mice than in BALB/c mice. These data suggest that systemic and local Th2 cytokine responses, especially those involving IL-5, are predominant in A. cantonensis-infected mice and that IL-5 is an important cytokine underlying the innate resistance of the mouse against A. cantonensis.

Eosinophilia of the cerebrospinal fluid (CSF) in permissive (rats) and non-permissive (mice) hosts infected with Angiostrongylus cantonensis, and the possible mechanism of the eosinophilia were studied. In three strains of thymic mice (ICR, ddY and BALB/c), the infection provoked a marked CSF eosinophilia starting at around day 12, reaching a peak level at day 20 and maintaining significantly high levels until day 35. In contrast, in athymic nude mice of BALB/c strain the infection failed to evoke this eosinophilia, suggesting T-cell dependence of murine CSF eosinophilia. Humoral antibodies did not correlate with the induction of eosinophilia. A time-course study of worm recovery in the mouse brains indicated a gradual but consistent reduction in worm burden in accordance with the rapid rise in CSF eosinophil levels. Bone marrow eosinophilia occurred in mice at day 5, which preceded CSF eosinophilia. Jirds, a permissive but less susceptible host, developed a CSF eosinophilia with a peak level at day 17, but which declined rapidly following the peak. Permissive rat hosts developed significant peripheral and bone marrow eosinophilia at day 35 but their CSF eosinophilia was markedly less prominent than that of mice and jirds. These data clearly indicate that there are distinct differences in the mechanism of eosinophilia and eosinophilia-inducing factors between permissive and non-permissive hosts.