Marianne Quiding-Järbrink

Differential expression of tissue-specific adhesion molecules on human circulating antibody-forming cells after systemic, enteric, and nasal immunizations. A molecular basis for the compartmentalization of effector B cell responses.

Expression of the adhesion molecules CD44, L-selectin (CD62L), and integrin alpha 4 beta 7 by antibody-secreting cells (ASC) was examined in human volunteers after oral, rectal, intranasal, or systemic immunization with cholera toxin B subunit. Almost all blood ASC, irrespective of immunization route, isotype (IgG and IgA), and immunogen, expressed CD44. On the other hand, marked differences were observed between systemically and intestinally induced ASC with respect to expression of integrin alpha 4 beta 7 and L-selectin, adhesion molecules conferring tissue specificity for mucosal tissues and peripheral lymph nodes, respectively. Thus, most ASC induced at systemic sites expressed L-selectin, whereas only a smaller proportion of ASC expressed alpha 4 beta 7. In contrast, virtually all IgA- and even IgG-ASC detected after peroral and rectal immunizations expressed alpha 4 beta 7, with only a minor fraction of these cells expressing L-selectin. Circulating ASC induced by intranasal immunization displayed a more promiscuous pattern of adhesion molecules, with a large majority of ASC coexpressing L-selectin and alpha 4 beta 7. These results demonstrate that circulating ASC induced by mucosal and systemic immunization express different sets of adhesion molecules. Furthermore, these findings provide for the first time evidence for differential expression of adhesion molecules on circulating ASC originating from different mucosal sites. Collectively, these results may explain the anatomical division of mucosal and systemic immune responses in humans as well as the compartmentalization of mucosal immune responses initiated in the upper vs. the lower aerodigestive tract.

DC-derived IL-18 drives Treg differentiation, murine Helicobacter pylori–specific immune tolerance, and asthma protection

Persistent colonization with the gastric bacterial pathogen Helicobacter pylori causes gastritis and predisposes infected individuals to gastric cancer. Conversely, it is also linked to protection from allergic, chronic inflammatory, and autoimmune diseases. We demonstrate here that H. pylori inhibits LPS-induced maturation of DCs and reprograms DCs toward a tolerance-promoting phenotype. Our results showed that DCs exposed to H. pylori in vitro or in vivo failed to induce T cell effector functions. Instead, they efficiently induced expression of the forkhead transcription factor FoxP3, the master regulator of Tregs, in naive T cells. Depletion of DCs in mice infected with H. pylori during the neonatal period was sufficient to break H. pylori-specific tolerance. DC depletion resulted in improved control of the infection but also aggravated T cell-driven immunopathology. Consistent with the mouse data, DCs infiltrating the gastric mucosa of human H. pylori carriers exhibited a semimature DC-SIGN(+)HLA-DR(hi)CD80(lo)CD86(lo) phenotype. Mechanistically, the tolerogenic activity of H. pylori-experienced DCs was shown to require IL-18 in vitro and in vivo; DC-derived IL-18 acted directly on T cells to drive their conversion to Tregs. CD4(+)CD25(+) Tregs from infected wild-type mice but not Il18(-/-) or Il18r1(-/-) mice prevented airway inflammation and hyperresponsiveness in an experimental model of asthma. Taken together, our results indicate that tolerogenic reprogramming of DCs ensures the persistence of H. pylori and protects against allergic asthma in a process that requires IL-18.

Production of Matrix Metalloproteinases in Response to Mycobacterial Infection

ABSTRACT Matrix metalloproteinases (MMPs) constitute a large family of enzymes with specificity for the various proteins of the extracellular matrix which are implicated in tissue remodeling processes and chronic inflammatory conditions. To investigate the role of MMPs in immunity to mycobacterial infections, we incubated murine peritoneal macrophages with viable Mycobacterium bovis BCG or Mycobacterium tuberculosis H37Rv and assayed MMP activity in the supernatants by zymography. Resting macrophages secreted only small amounts of MMP-9 (gelatinase B), but secretion increased dramatically in a dose-dependent manner in response to either BCG or M. tuberculosis in vitro. Incubation with mycobacteria also induced increased MMP-2 (gelatinase A) activity. Neutralization of tumor necrosis alpha (TNF-α), and to a lesser extent interleukin 18 (IL-18), substantially reduced MMP production in response to mycobacteria. Exogenous addition of TNF-α or IL-18 induced macrophages to express MMPs, even in the absence of bacteria. The immunoregulatory cytokines gamma interferon (IFN-γ), IL-4, and IL-10 all suppressed BCG-induced MMP production, but through different mechanisms. IFN-γ treatment increased macrophage secretion of TNF-α but still reduced their MMP activity. Conversely, IL-4 and IL-10 seemed to act by reducing the amount of TNF-α available to the macrophages. Finally, infection of BALB/c or severe combined immunodeficiency (SCID) mice with either BCG or M. tuberculosis induced substantial increases in MMP-9 activity in infected tissues. In conclusion, we show that mycobacterial infection induces MMP-9 activity both in vitro and in vivo and that this is regulated by TNF-α, IL-18, and IFN-γ. These findings indicate a possible contribution of MMPs to tissue remodeling processes that occur in mycobacterial infections.

Induction of B cell responses in the stomach of Helicobacter pylori- infected subjects after oral cholera vaccination.

We have evaluated the possibility of inducing antibody responses locally in the human stomach as a prerequisite for the development of a vaccine against Helicobacter pylori. Both H. pylori-infected and noninfected subjects were immunized with an oral B subunit whole cell (BS-WC) cholera vaccine, and total and vaccine-specific antibody-secreting cells (ASC) were determined by the enzyme-linked immunospot (ELISPOT) technique in cells isolated from the antrum and duodenum, respectively, before and after vaccination. Most of the subjects responded to the vaccination with high frequencies of vaccine-specific ASCs in the duodenum as well as high-serum antibody titers, and no significant differences were seen in the responses between H. pylori- infected and noninfected subjects. When studying the gastric mucosa, on the other hand, there were dramatic differences between the H. pylori-infected and the noninfected subjects. Thus, whereas none of the noninfected subjects responded to the immunization in antrum, most of the H. pylori-infected subjects had high frequencies of vaccine-specific ASCs in this location after vaccination. Furthermore, the H. pylori-infected subjects had strikingly higher (as a mean 80-fold) frequencies of total IgA-secreting cells in antrum than the noninfected subjects, whereas the frequencies of total IgA-secreting cells in the duodenum were comparable between the groups. In conclusion, these results demonstrate the possibility of inducing antibody responses locally in the gastric mucosa of H. pylori-infected individuals, a finding with obvious implications for the future development of a therapeutic vaccine against H. pylori.

Dynamic Development of Homing Receptor Expression and Memory Cell Differentiation of Infant CD4+CD25high Regulatory T Cells

Migration of CD4+CD25+FOXP3+ regulatory T cells (Treg) is important for suppressing immune responses in different tissues. Previous studies show that the majority of Treg at birth express gut homing receptor α4β7 and that only few express CCR4, while the reverse pattern is found in adults. The age at which homing receptor switch occurs in vivo is not known. In this study, we show, in a prospective study of human infants from birth to 3 years of age, that homing receptor switch from α4β7 to CCR4 commences between 1 1/2 and 3 years of age and that Treg at that age also had started their switch to a memory phenotype. The majority of naive Treg express α4β7 in infants but not in adults, while the majority of memory Treg express CCR4 both infants and adults. The homing receptor expression on Treg corresponds to their actual migration properties, because Treg from cord blood migrate foremost toward the gut-associated chemokine CCL25. CD4+FOXP3+ T cell numbers increase rapidly in the circulation during the first days of life indicating conversion to suppressive Treg from CD25high Treg precursors. These findings suggest that the gut is the primary site of Treg stimulation to exogenous Ags during the first 18 mo of life and that homing receptor switch toward a more extra-intestinal phenotype occurs thereafter.

Enhanced M1 Macrophage Polarization in Human Helicobacter pylori-Associated Atrophic Gastritis and in Vaccinated Mice

Background Infection with Helicobacter pylori triggers a chronic gastric inflammation that can progress to atrophy and gastric adenocarcinoma. Polarization of macrophages is a characteristic of both cancer and infection, and may promote progression or resolution of disease. However, the role of macrophages and their polarization during H. pylori infection has not been well defined. Methodology/Principal Findings By using a mouse model of infection and gastric biopsies from 29 individuals, we have analyzed macrophage recruitment and polarization during H. pylori infection by flow cytometry and real-time PCR. We found a sequential recruitment of neutrophils, eosinophils and macrophages to the gastric mucosa of infected mice. Gene expression analysis of stomach tissue and sorted macrophages revealed that gastric macrophages were polarized to M1 after H. pylori infection, and this process was substantially accelerated by prior vaccination. Human H. pylori infection was characterized by a mixed M1/M2 polarization of macrophages. However, in H. pylori-associated atrophic gastritis, the expression of inducible nitric oxide synthase was markedly increased compared to uncomplicated gastritis, indicative of an enhanced M1 macrophage polarization in this pre-malignant lesion. Conclusions/Significance These results show that vaccination of mice against H. pylori amplifies M1 polarization of gastric macrophages, and that a similar enhanced M1 polarization is present in human H. pylori-induced atrophic gastritis.

Accumulation of CCR4+ CTLA-4hi FOXP3+CD25hi Regulatory T Cells in Colon Adenocarcinomas Correlate to Reduced Activation of Conventional T Cells

Background Colorectal cancer usually gives rise to a specific anti-tumor immune response, but for unknown reasons the resulting immunity is not able to clear the tumor. Recruitment of activated effector lymphocytes to the tumor is important for efficient anti-tumor responses, while the presence of regulatory T cells (Treg) down-modulate tumor-specific immunity. We therefore aimed to determine homing mechanisms and activation stage of Treg and effector T cell infiltrating colon tumors compared to cells from the unaffected mucosa in patients suffering from colon adenocarcinoma. Methodology/Principal Findings Lymphocytes were isolated from unaffected and tumor mucosa from patients with colon adenocarcinoma, and flow cytometry, immunohistochemistry, and quantitative PCR was used to investigate the homing mechanisms and activation stage of infiltrating Treg and conventional lymphocytes. We detected significantly higher frequencies of CD25highFOXP3+CD127low putative Treg in tumors than unaffected mucosa, which had a complete demethylation in the FOXP3 promotor. Tumor-associated Treg had a high expression of CTLA-4, and some appeared to be antigen experienced effector/memory cells based on their expression of αEβ7 (CD103). There were also significantly fewer activated T cells and more CTLA-4+ conventional T cells susceptible to immune regulation in the tumor-associated mucosa. In contrast, CD8+granzyme B+ putative cytotoxic cells were efficiently recruited to the tumors. The frequencies of cells expressing α4β7 and the Th1 associated chemokine receptor CXCR3 were significantly decreased among CD4+ T cells in the tumor, while frequencies of CD4+CCR4+ lymphocytes were significantly increased. Conclusions/Significance This study shows that CCR4+CTLA4hi Treg accumulate in colon tumors, while the frequencies of activated conventional Th1 type T cells are decreased. The altered lymphocyte composition in colon tumors will probably diminish the ability of the immune system to effectively attack tumor cells, and reducing the Treg activity is an important challenge for future immunotherapy protocols.

Human IgA‐secreting cells induced by intestinal, but not systemic, immunization respond to CCL25 (TECK) and CCL28 (MEC)

Organ‐specific homing of lymphoid cells depends on the expression of tissue‐specific adhesion molecules and production of specific chemokines. CCL25 (TECK) and CCL28 (MEC) have been reported to direct circulating memory/effector B cells to mucosal tissues. Here, we examined if differential responsiveness to mucosal and systemic chemokines could explain the differential migration pattern of circulating human antibody‐secreting cells (ASC), induced by mucosal and systemic immunization. There was a robust migration of specific IgA‐ and IgM‐ASC induced by Salmonella vaccination toward the mucosal chemokines CCL25 and CCL28. In contrast, tetanus‐specific ASC migrated to the systemic chemokine CXCL12 (SDF‐1α) and showed no response to CCL25 or CCL28, not even tetanus‐specific IgA‐ASC. Cell sorting experiments demonstrated that Salmonella‐specific ASC co‐expressed CCR9 and CCR10. Our results show that induction site, rather than isotype commitment, determines the chemokine responsiveness and migration pattern of human effector B cells.

Human Mucosa-Associated Invariant T Cells Accumulate in Colon Adenocarcinomas but Produce Reduced Amounts of IFN-γ

Mucosa-associated invariant T (MAIT) cells are innate-like T cells with a conserved TCR α-chain recognizing bacterial metabolites presented on the invariant MHC-related 1 molecule. MAIT cells are present in intestinal tissues and liver, and they rapidly secrete IFN-γ and IL-17 in response to bacterial insult. In colon cancer, IL-17–driven inflammation promotes tumor progression, whereas IFN-γ production is essential for antitumor immunity. Thus, tumor-associated MAIT cells may affect antitumor immune responses by their secreted cytokines. However, the knowledge of MAIT cell presence and function in tumors is virtually absent. In this study, we determined the frequency, phenotype, and functional capacity of MAIT cells in colon adenocarcinomas and unaffected colon lamina propria. Flow cytometric analyses showed significant accumulation of MAIT cells in tumor tissue, irrespective of tumor stage or localization. Colonic MAIT cells displayed an activated memory phenotype and expression of chemokine receptors CCR6 and CCR9. Most MAIT cells in unaffected colon tissues produced IFN-γ, whereas only few produced IL-17. Colonic MAIT cells also produced TNF-α, IL-2, and granzyme B. In the tumors, significantly lower frequencies of IFN-γ–producing MAIT cells were seen, whereas there were no differences in the other cytokines analyzed, and in vitro studies showed that secreted factors from tumor tissue reduced IFN-γ production from MAIT cells. In conclusion, MAIT cells infiltrate colon tumors but their ability to produce IFN-γ is substantially reduced. We suggest that MAIT cells have the capacity to promote local immune responses to tumors, but factors in the tumor microenvironment act to reduce MAIT cell IFN-γ production.

CD4+CD25high regulatory T cells reduce T cell transendothelial migration in cancer patients

Cell‐mediated immunity is thought to be the main mechanism of anti‐tumour responses of the host, but it is not known if cancer disease affects T cell recruitment from blood to tissues. Therefore, we compared Heliobacter pylori‐induced T cell transendothelial migration (TEM) in H. pylori‐infected gastric carcinoma patients, colon and lung carcinoma patients and healthy volunteers. H. pylori induced significant T cell migration from all groups. However, there was a dramatic reduction of T cell TEM in gastric carcinoma patients (80%) compared to healthy individuals. A similarly reduced transmigration was also seen in colon and lung carcinoma patients. We found significantly increased frequencies of Treg cells in the blood of gastric carcinoma patients compared to healthy individuals, and depletion of Treg cells from the blood of these patients prior to TEM restored T cell migration. The effect of Treg cells was largely dependent on cell‐cell contact, but not on IL‐10 or TGF‐β. In addition, the presence of Treg cells led to reduced T cell attachment to endothelium and decreased production of T cell‐recruiting chemokines during TEM. In conclusion, Treg cell‐mediated reduction of T cell TEM may reduce T cell recruitment in patients with epithelial malignancies, thereby hampering anti‐tumour responses.