Nonspecific enhancement of mouse antihapten IgE antibody response: involvement of a T-cell subpopulation and its product for the potentiation

A potential role of interleukin 18 in severe falciparum malaria

Interleukin-18 (IL-18) is a potent proinflammatory cytokine that induces interferon-gamma (IFN-gamma) production from Th1 cells, NK cells and activated macrophages, particularly in the presence of IL-12. However, it is also shown that without help from IL-12, IL-18 is capable of inducing IL-4 and IL-13 production in T cells, NK cells, mast cells and basophils, and that administration of IL-18 in conjunction with an allergen increases serum IgE levels. In order to clarify the role of IL-18 in disease severity of falciparum malaria, we have examined serum levels of IL-18, IFN-gamma, and IgE for 96 patients with falciparum malaria [Trans. R. Soc. Trop. Med. Hyg. 97, 236-241]. Results suggested that IL-18 plays a key role in inducing severe malaria through a pathway of elevating IFN-gamma, rather than its IgE inducing activity. Based on these results, the role of IL-18 in severe falciparum malaria will be discussed in this review.

Involvement of interleukin-18 in severe Plasmodium falciparum malaria

Serum levels of interleukin-18 (IL-18), interferon-gamma (IFN-gamma), and immunoglobulin E (IgE) were determined for 96 patients with Plasmodium falciparum malaria admitted to hospital, Bangkok, Thailand in the period 1998-2000. The patients were divided into 3 groups, i.e. uncomplicated, severe and cerebral malaria according to WHO criteria (2000). Elevation of IL-18 levels was observed in all 3 groups, with a tendency for higher levels in cases with severe malaria throughout the course of the disease. Moreover, there was a significant correlation between IL-18 levels and the extent of parasitaemia among patients with severe malaria. However, IL-18 levels decreased more significantly in patients with cerebral malaria compared with the other groups in the late stage of the disease. Elevated levels of IFN-gamma were also observed in all groups of patients, especially in those with severe or cerebral malaria, and the levels in patients with cerebral malaria remained significantly higher than in those with uncomplicated malaria during days 4-7 post-treatment, suggesting the involvement of IFN-gamma in disease severity. Meanwhile, no significant difference was observed in IgE levels between the severe and uncomplicated groups of patients with helminth infection, although IgE levels were significantly higher in helminth-infected patients than uninfected patients. These results suggest that IL-18 plays a key role in inducing severe malaria through another pathway, such as elevation of IFN-gamma, rather than its IgE inducing activity.

Sex-dependent differences in the IgE response modulated by phytohemagglutinin

Modulation of the IgE response by PHA treatment in relation to animal sex was analysed. Male and female RF mice were immunized with ovalbumin in aluminum hydroxide gel and PHA was injected 1 or 2 days before immunization. Castrated mice were also immunized and received PHA on day -2. The results show that the IgE response is lower in the male than in the female group. An opposite class specific modulation depending on the timing of the PHA inoculation is observed between males and females. This effect is not observed in castrated mice. IgM and/or IgG production is neither modified by sex nor by the mitogen treatment.

Allergic predisposition among infants with bronchiolitis

Allergic predisposition among infants with bronchiolitis was examined. The number of infants with serum IgE exceeding mean +1 SD was 31/70 (44.3%). The rate of positive radioallergosorbent test (RAST) scores of 1 or more to mites, egg white, or milk was 31/71 (43.7%) and that of scores over 2 was 11/71 (15.5%). Eosinophils and/or mast cells were found in their nasal smears on several occasions. These results indicated that allergic predisposition may be observed among infants with bronchiolitis.

Immunomodulation by nematodes: a review

There is current evidence that infections with Trichinella spiralis, Ascaris suum, Nippostrongylus brasiliensis, Nematospiroides dubius (syn. Heligmosomoides polygyrus) and diverse filariae affect the immune responsiveness of their hosts. T. spiralis, or its extracts, can depress or enhance the heterologous humoral or cell-mediated immunities, and affect macrophage activity or the response to other invaders. These effects are induced by products of the migratory and early muscle larvae and appear to obey more than one single-mechanism. A suum acute infections or extracts depress responses involving T cell activity, but stimulate polygonal expansion of B-cells. Nippostrongylus brasiliensis causes polyclonal stimulation of IgE-producing cells, enhances immune responses during the first week of infection and inhibits them later on. Nematospiroides dubius depresses homologous and heterologous immunity and facilitates the permanence of other intestinal nematodes. Filarial worms appear to depress the homologous cell-mediated immunity and the heterologous humoral response by induction of suppressor cells and humoral factors. These phenomena are probably the result of evolutionary pressures on the parasites that facilitate their survival. In the host, they are likely to aggravate the homologous infection, facilitate intercurrent conditions and interfere with immunoprophylaxis procedures.

Associations between HLA and immune responses in individuals with chronic schistosomiasis japonica

The association of an HLA specificity with low or high immune responsiveness to Schistosoma japonicum antigen (Sj) was demonstrated among individuals who had previously been exposed to S. japonicum infection. The frequency of HLA-Aw24 specificity among low responders in the IgG antibody response determined by the enzyme-linked immunosorbent assay (ELISA) was higher than that among high responders. Significant association between HLA-B7 and high responsiveness was observed in the IgE antibody response. The frequency of HLA-Bw52-Dw12 was also found to increase among individuals with higher levels of total serum IgE. These results suggest that antibody responses to Sj are regulated by an immune response (Ir) gene(s) linked to the major histocompatibility complex (MHC), although a possibility of the presence of non-MHC-linked Ir genes is not excluded. Serum IgE levels may also be controlled by a gene(s) linked to the MHC.

Inhibitory effects of a new antiallergic agent, azelastine, on passive cutaneous anaphylaxis and expulsion of Nippostrongylus brasiliensis

A new antiallergic agent, 4-(p-chlorobenzyl)-2-[N-methyl-perhydroazepinyl-(4)]-1-(2H)-phthalazinone hydrochloride (azelastine), was found to exert inhibitory effects on passive cutaneous anaphylaxis in the rat and on expulsion of Nippostrongylus brasiliensis from the rat intestine when this agent was administered intravenously at appropriate doses.