IL-12 affects Dermatophagoides farinae-induced IL-4 production by T cells from pediatric patients with mite-sensitive asthma

Dermatophagoides-induced interleukin-10 production by peripheral blood lymphocytes from patients with asthma in remission

Interleukin (IL)-10 is a cytokine that regulates inflammatory responses. We studied the role of IL-10 in the development of tolerance to Dermatophagoides farinae in asthma patients in remission, since asthma improves in most children during adolescence. The spontaneous production of IL-10 by cultured peripheral blood mononuclear cells (PBMC) was higher in patients with active asthma than in normal subjects. IL-10 production decreased when 1 microg/ml D. farinae was added to cultures, but increased again in a dose-dependent manner when higher concentrations of D. farinae were added. In patients with remission of asthma, IL-10 production was lower than in patients with active asthma. However, production of IL-10 showed a reciprocal increase in the presence of 1 microg/ml D. farinae, and decreased again at 10 and 50 microg/ml D. farinae. Such alterations were not observed in normal subjects. Cell lines established from patients asthma in remission showed higher IL-10 production when compared with that by cell lines from normal subjects or patients with active asthma when the cells were stimulated by D. farinae at 1 or 10 microg/ml. Neutralization of IL-10 led to revival of the D. farinae-specific proliferative response of PBMC from patients in remission, which was otherwise decreased. The increase of IL-10 production stimulated by D. farinae was inhibited by addition of an anti-IL-10 antibody. In contrast, antigen-induced interferon (IFN)-gamma production, which was increased by D. farinae stimulation when patients were in remission, did not increase after treatment with anti-IL-10, although spontaneous IFN-gamma production increased to the level seen after D. farinae stimulation. The reduced IL-4 production by cells from patients in remission after stimulation with D. farinae antigen, which was significantly higher in active patients, was not reversed by neutralization of IL-10. The D. farinae-induced IL-10/IL-4 production ratio, but not the IL-10/IL-5 production ratio, may be a significant indicator for evaluation of whether a patient has been in remission. In conclusion, D. farinae-specific anergy of T cells is likely to be induced by increased levels of IL-10 and IFN-gamma that are initially produced by specific T cells after exposure to relevant mite allergen in patients in remission.

Roxithromycin promotes lymphocyte apoptosis in Dermatophagoides-sensitive asthma patients

A new macrolide, roxithromycin, may be an effective treatment for asthma. Lymphocyte apoptosis is impaired in patients with asthma, while spontaneous apoptosis increases during remission, and such changes may be involved in the onset and remission of mite-sensitive asthma. Lymphocyte apoptosis was evaluated by incubating cells from patients with asthma in the presence of roxithromycin. Low concentrations of roxithromycin (1-500 ng/ml) augmented the early, but not late, phase of apoptosis in Dermatophagoides farinae-stimulated peripheral blood mononuclear (PBM) cells, while high concentrations of roxithromycin (1 microg/ml; 6 microg/ml is the maximum serum level) augmented both the early and late phases of apoptosis. In both unstimulated and phytohemagglutinin-stimulated cells, roxithromycin did not significantly affect the induction of apoptosis. In cells from normal subjects, roxithromycin did not affect the induction of apoptosis. Other antibiotics, including cefazolin and ampicillin, did not cause significant induction of apoptosis. Fas ligand, but not Fas receptor, expression on D. farinae-stimulated cells was up-regulated after stimulation with 1 microg/ml roxithromycin, while Bcl-2 expression on both unstimulated and D. farinae-stimulated cells showed a decrease after the same treatment. Roxithromycin can induce apoptosis of D. farinae-activated lymphocytes in patients with D. farinae-sensitive asthma. Induction of the Fas/Fas ligand system and reduced Bcl-2 expression were involved in the promotion of apoptosis by roxithromycin treatment.

Immunomodulatory effects of CpG oligodeoxynucleotides on established th2 responses

CpG oligodeoxynucleotides (CpG ODNs) are known to induce type 1 T-helper-cell (Th1) responses. We have previously demonstrated that CpG ODNs administered during sensitization prevent Th2-mediated eosinophilic airway inflammation in vivo. We also reported that key Th1 cytokines, gamma interferon (IFN-gamma) and interleukin 12 (IL-12), are not necessary for this protection. Recent in vivo data suggest that CpG ODNs might also reverse established pulmonary eosinophilia. In order to clarify how CpG ODNs can inhibit established Th2 responses, we evaluated the cytokine production from splenocytes from antigen- and alum-immunized mice. Restimulation with antigen induced IL-5, which was clearly inhibited by coculture with CpG ODNs in a concentration-dependent manner. CpG ODNs also induced IFN-gamma, but in a concentration-independent manner. The inhibition of IL-5 production was not mediated through natural killer cells or via CD8(+) T lymphocytes. Although IFN-gamma plays an important role in inhibition of antigen-induced IL-5 production by CpG ODNs, IFN-gamma was not the sole factor in IL-5 inhibition. CpG ODNs also induced IL-10, and this induction correlated well with IL-5 inhibition. Elimination of IL-10 reduced the anti-IL-5 effect of CpG ODNs, although incompletely. This may be because IFN-gamma, induced by CpG ODNs, is also inhibited by IL-10, serving as a homeostatic mechanism for the Th1-Th2 balance. Overproduction of IFN-gamma was downregulated by CpG ODN-induced IL-10 via modulation of IL-12 production. These data suggest that CpG ODNs may inhibit established Th2 immune responses through IFN-gamma and IL-10 production, the latter serving to regulate excessive Th1 bias. These properties of CpG ODNs might be a useful feature in the development of immunotherapy adjuvants against allergic diseases such as asthma.