The eosinophil is a central effector cell in allergic asthma. Differentiation and function of eosinophils is regulated by interleukin (IL)‐3, IL‐5 and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), which all signal through a common β receptor subunit (βc). Recent therapeutic approaches targeting IL‐5 alone have had limited effects on disease progression. By employing mice lacking the βc and βIL‐3 receptor subunits we were able to interrupt signalling through all three eosinophilopoietic cytokines and prevent allergen‐induced expansion and accumulation of eosinophils in the lung in a mouse model of allergic airways inflammation. Moreover, βc deficiency resulted in inhibition of hallmark features of asthma including airways hypersensitivity, mucus hypersecretion and antigen‐specific IgE. Surprisingly, we also identified a critical role for the βc in regulating type 2 immunity. Th2 cells in the lung of allergen‐challenged βc−/− mice were limited in their ability to proliferate, produce cytokines and migrate to effector sites, which was attributed to reduced numbers of myeloid dendritic cells in the lung compartment. Thus the βc subunit plays a critical role in allergen‐induced eosinophil responses and is pivotal in regulating molecules that promote both early and late phases of allergic inflammation, representing a novel target for therapy. (Supported by the NIH and NHMRC)

Chlamydia trachomatis is an obligate intracellular bacterial pathogen that infects the genital and ocular mucosa of humans, causing infections that can lead to pelvic inflammatory disease, infertility, and blinding trachoma. C. pneumoniae is a respiratory pathogen that is the cause of 12-15% of community-acquired pneumonia. Both chlamydial species were believed to be restricted to the epithelia of the genital, ocular, and respiratory mucosa; however, increasing evidence suggests that both these pathogens can be isolated from peripheral blood of both healthy individuals and patients with inflammatory conditions such as coronary artery disease and asthma. Chlamydia can also be isolated from brain tissues of patients with degenerative neurological disorders such as Alzheimer's disease and multiple sclerosis, and also from certain lymphomas. An increasing number of in vitro studies suggest that some chlamydial species can infect immune cells, at least at low levels. These infections may alter immune cell function in a way that promotes chlamydial persistence in the host and contributes to the progression of several chronic inflammatory diseases. In this paper, we review the evidence for the growth of Chlamydia in immune cells, particularly monocytes/macrophages and dendritic cells, and describe how infection may affect the function of these cells.

No abstract

There is strong epidemiological evidence that Chlamydia infection can lead to exacerbation of asthma. However, the mechanism(s) whereby chlamydial infection, which normally elicits a strong Th type 1 (Th1) immune response, can exacerbate asthma, a disease characterized by dominant Th type 2 (Th2) immune responses, remains unclear. In the present study, we show that Chlamydia muridarum infection of murine bone marrow-derived dendritic cells (BMDC) modulates the phenotype, cytokine secretion profile, and Ag-presenting capability of these BMDC. Chlamydia-infected BMDC express lower levels of CD80 and increased CD86 compared with noninfected BMDC. When infected with Chlamydia, BMDC secrete increased TNF-α, IL-6, IL-10, IL-12, and IL-13. OVA peptide-pulsed infected BMDC induced significant proliferation of transgenic CD4+ DO11.10 (D10) T cells, strongly inhibited IFN-γ secretion by D10 cells, and promoted a Th2 phenotype. Intratracheal transfer of infected, but not control noninfected, OVA peptide-pulsed BMDC to naive BALB/c mice, which had been i.v. infused with naive D10 T cells, resulted in increased levels of IL-10 and IL-13 in bronchoalveolar lavage fluid. Recipients of these infected BMDC showed significant increases in airways resistance and decreased airways compliance compared with mice that had received noninfected BMDC, indicative of the development of airways hyperreactivity. Collectively, these data suggest that Chlamydia infection of DCs allows the pathogen to deviate the induced immune response from a protective Th1 to a nonprotective Th2 response that could permit ongoing chronic infection. In the setting of allergic airways inflammation, this infection may then contribute to exacerbation of the asthmatic phenotype.

The precise role of antigen-presenting cells (APC) in regulating the balance of T-helper type 1 (Th1) and T-helper type 2 (Th2) cytokine production is unclear. Dendritic cells (DC), the most potent APC for activation of naive T cells, were found to regulate Th1 and Th2 cytokine profiles in a fashion dependent upon their tissue of origin. Spleen (systemic) DC induce mainly Th1 cytokines and Peyer's patch (mucosal) DC induce predominantly Th2 cytokines. These findings support the current concept that different tissues, each with its distinct microenvironment of cytokines, hormones, and cellular elements, are involved in the selection, promotion, and/or maintenance of different immune responses. With regard to DC, it is apparent that the tissue of DC origin determines the cytokine profiles produced by T cells and that DC from different tissues favor either cellular versus humoral immune responses by influencing T cell cytokine production.

The mechanisms of wound healing in the gut are poorly understood but are mediated by cytokines in other tissues. In this study we wanted to determine which cytokines were expressed after nonspecific colonic injury, the kinetics of that expression, and how cytokine expression correlated with tissue histology. At 0, 4, 8, 12, 24, 48, and 72 h after intrarectal administration of 3% acetic acid to C3H/HeJ mice, their colons were removed for histology, organ culture, and RNA extraction. Cytokine mRNA expression for various cytokines was assessed by reverse transcriptase-polymerase chain reaction with primers specific for each cytokine. Cytokine production in organ cultures was measured with bioassays. Shortly after colonic injury and during colonic regeneration, proinflammatory cytokines such as interleukin-1 beta (IL-1 beta), IL-6, tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein (MIP), and transforming growth factor-beta (TGF-beta) were expressed. In contrast, expression of T cell-derived cytokines was not detected at any time point. Cytokines such as IL-1 beta, IL-6, IL-10, TNF-alpha, and MIP-1 are important mediators of tissue repair and restitution after nonspecific colonic injury and may subserve a similar role in human colitis.

Intranasal (i.n.) immunization with bacterial protein antigens coupled to cholera toxin B subunit (CTB) effectively induces mucosal, especially salivary immunoglobulin A (IgA), and nonmucosal antibody responses in mice. To examine the regional distribution of antigen-specific B and T cells after i.n. immunization, antibody-secreting cells and antigen-responsive T cells in cervical lymph nodes (CLN) were compared with those found after intraoral or subcutaneous (in the neck) administration of the same antigen and with T cells found in mesenteric lymph nodes (MLN) and spleen after intragastric immunization. The i.n. immunization induced predominantly IgA antibody-secreting cells in salivary glands and IgA and IgG antibody-secreting cells in the superficial and central CLN; these responses were quantitatively enhanced if the antigen was coupled to CTB. Intraoral immunization also induced IgA and IgG antibody-secreting cells in the superficial and central CLN, but only if intact cholera toxin was included as an adjuvant. In contrast, subcutaneous (neck) immunization induced IgG antibody-secreting cells mainly in the draining facial lymph nodes. CLN cell populations resembled those of MLN, except that CLN lymphocytes had higher proportions of T cells and lower proportions of B cells and a slightly higher CD4 ؉ /CD8 ؉ ratio among T cells than the MLN lymphocytes did. T cells that proliferated in response to antigen in vitro were found especially in central CLN 2 days after i.n. immunization and persisted for up to 6 months, whereas after intragastric immunization, responsive T cells were not found in the MLN for up to 14 days. After culture with antigen in vitro, T cells from the superficial CLN of i.n. immunized mice secreted both gamma interferon and interleukin-4. Therefore, after i.n. immunization, superficial and central CLN represent sites of regional lymphocyte development, and the central CLN in particular appear to be sites where memory T cells persist.

Atrophic gastritis caused by Helicobacter pylori is the precursor lesion in the development of intestinal-type gastric adenocarcinoma. In animal models, atrophic gastritis induced by Helicobacter felis has been shown to be host dependent, developing in some mouse strains and not in others. The lipopolysaccharide (LPS) of H. pylori has been suggested to play a role in the induction of gastritis. The goal of this study was to compare the inflammation induced by long-term infection of the C3H/He and the C3H/HeJ strains of mice with H. felis. C3H/HeJ mice are unresponsive to LPS. Six months after infection, severe atrophic gastritis had developed in the body mucosae of all infected C3H/He mice, with replacement of parietal and chief cells. Atrophy was associated with a loss of the H. felis from the antral mucosa. In contrast, no atrophy was seen in the infected C3H/HeJ non-LPS responder animals, and heavy colonization of the antrum remained. There were no significant differences between both the quantitative and qualitative serum immunoglobulin G (IgG) and salivary IgA levels in both strains of mice. The main difference between the two strains of long-term-infected mice was a lack of macrophage infiltration in the lamina propria. Immunization induced good protective immunity to challenge with viable H. felis. Helicobacter-induced, host-dependent gastritis is likely to be cell mediated. The C3H/He and C3H/HeJ mouse model provides an excellent opportunity to investigate the cellular basis of atrophic gastritis.