Advances in the Knowledge of the Underlying Airway Remodeling Mechanisms in Chronic Rhinosinusitis Based on the Endotypes: A Review.

Chronic rhinosinusitis (CRS) is a chronic inflammatory condition of the nasal and paranasal sinus mucosa that affects up to 10% of the population worldwide. CRS is the most representative disease of the upper respiratory tract where airway remodeling occurs, including epithelial damage, thickening of the basement membrane, fibrosis, goblet cell hyperplasia, subepithelial edema, and osteitis. CRS is divided into two phenotypes according to the presence or absence of nasal polyps: CRS with nasal polyp (CRSwNP) and CRS without nasal polyps (CRSsNP). Based on the underlying pathophysiologic mechanism, CRS is also classified as eosinophilic CRS and non-eosinophilic CRS, owing to Type 2 T helper (Th2)-based inflammation and Type 1 T helper (Th1)/Type 17 T helper (Th17) skewed immune response, respectively. Differences in tissue remodeling in CRS are suggested to be based on the clinical phenotype and endotypes; this is because fibrosis is prominent in CRSsNP, whereas edematous changes occur in CRSwNP, especially in the eosinophilic type. This review aims to summarize the latest information on the different mechanisms of airway remodeling in CRS according to distinct endotypes.

Thymic stromal lymphopoietin drives the development of IL-13+ Th2 cells.

T helper 2 (Th2) cells are pivotal in the development of allergy. Allergen exposure primes IL-4+ Th2 cells in lymph node, but production of effector cytokines including IL-5 and IL-13 is thought to require additional signals from antigen and the environment. Here we report that a substantial proportion of naive CD4+ T cells in spleen and lymph node express receptors for the epithelium-derived inflammatory cytokine thymic stromal lymphopoietin (TSLP). Culture of naive CD4+ T cells in anti-(a)CD3, aCD28, and TSLP-supplemented Th2 conditions enabled the development of a unique population of IL-13-single positive (IL-13-SP) CD4+ T cells; TSLP and Th2 conditions were both required for their development. Sorting experiments revealed that IL-13-SP Th2 cells originated from IL-4-negative precursors and coexpressed transcripts for the Th2 cytokines IL-5 and IL-9. In vivo, high TSLP levels acted directly on CD4+ T cells to induce the development of IL-13-SP and IL-4+IL-13+ double-positive populations in lymph node. These cells were phenotypically similar to Th2 effector cells and were CXCR5lowPD1low and expressed low levels of Bcl6 and Il21 transcripts and high levels of Gata3, Il3, and Il5 Our findings suggest a role of TSLP in directly promoting Th2 cell effector function and support the notion of TSLP as a key driver of Th2 inflammation.

CD4+ T helper 2 cells--microbial triggers, differentiation requirements and effector functions.

Over the past 10 years we have made great strides in our understanding of T helper cell differentiation, expansion and effector functions. Within the context of T helper type 2 (Th2) cell development, novel innate-like cells with the capacity to secrete large amounts of interleukin-5 (IL-5), IL-13 and IL-9 as well as IL-4-producing and antigen-processing basophils have (re)-emerged onto the type 2 scene. To what extent these new players influence αß+ CD4+ Th2 cell differentiation is discussed throughout this appraisal of the current literature. We highlight the unique features of Th2 cell development, highlighting the three necessary signals, T-cell receptor ligation, co-stimulation and cytokine receptor ligation. Finally, putting these into context, microbial and allergenic properties that trigger Th2 cell differentiation and how these influence Th2 effector function are discussed and questioned.

Aging is associated with a rapid decline in frequency, alterations in subset composition, and enhanced Th2 response in CD1d-restricted NKT cells from human peripheral blood.

NKT cells are important for initiating and regulating immune responses. We investigated the age-related changes in the CD1d-restricted semi-invariant NKT (iNKT) cells in peripheral blood of healthy adults. The iNKT cell frequency was 2.5- to 10.7-fold less in healthy elderly subjects (61 years and over) compared to the healthy young subjects (20-40 years, p<0.001). This age-related decline in iNKT cells was observed both in freshly isolated PBMC and in cultures where iNKT cells were enriched by alpha-GalCer stimulation using either the Valpha24/Vbeta11 TCR antibody pair or the CD1d-tetramer as the iNKT cell marker. The decline in frequency was associated with an alteration in the iNKT cell subset compositions: an increase in the proportion of CD4+ subset and a decrease in the proportion of CD4/CD8 double-negative (DN) subset. The age-related decline in iNKT cells and changes in subset composition were independent from the age-related changes of conventional T cells/T cell subsets. Additionally, there was a Th1 to Th2 shift in the cytokine response profile from iNKT cells with aging. We conclude that aging is associated with a significant decline in iNKT cell frequency in peripheral blood, accompanied with alterations in subset composition and cytokine response profile.

Human natural killer T cells are heterogeneous in their capacity to reprogram their effector functions.

BACKGROUND: Natural killer T (NKT) cells are a subset of T cells that help potentiate and regulate immune responses. Although human NKT cell subsets with distinct effector functions have been identified, it is unclear whether the effector functions of these subsets are imprinted during development or can be selectively reprogrammed in the periphery. RESULTS: We found that neonatal NKT cells are predominantly CD4+ and express higher levels of CCR7 and CD62L and lower levels of CD94 and CD161 than adult CD4+ or CD4- NKT cell subsets. Accordingly, neonatal NKT cells were more flexible than adult CD4+ NKT cells in their capacity to acquire Th1- or Th2-like functions upon either cytokine-mediated polarization or ectopic expression of the Th1 or Th2 transcription factors T-bet and GATA-3, respectively. Consistent with their more differentiated phenotype, CD4- NKT cells were predominantly resistant to functional reprogramming and displayed higher cytotoxic function. In contrast to conventional T cells, neither the expression of CXCR3 nor the cytotoxic capacity of neonatal NKT cells could be reprogrammed. CONCLUSIONS AND SIGNIFICANCE: Together, these results suggest that neonatal CD4+, adult CD4+, and adult CD4- NKT may represent unique states of maturation and that some functions of human NKT cells may be developmentally imprinted, while others are acquired similar to conventional T cell subsets during peripheral maturation and differentiation. Given the potent immuno-regulatory functions of NKT cells, these findings have important implications for the development of novel NKT cell-based therapeutics and vaccines.

Desnutrición primaria y competencia inmunológica. Verdadera inmunodeficiencia, polarización adaptativa hacia una respuesta Th2 o ambas? / Primary malnutrition and immunological competence. Real immunodeficiency, adaptive TH2-biased responses or both?

La asociación entre malnutrición e infección ha sido reconocida desde hace tiempo. En estudios de terreno se demostró que los individuos malnutridos presentan mayor cantidad de infecciones pulmonares y enterales y un aumento de la mortalidad en el largo plazo a consecuencia de infecciones. Las infecciones contribuyen a empeorar el estado nutricional, y la malnutrición favorece la ocurrencia de infecciones. El hacinamiento, la mala calidad y conservación de los alimentos, su contaminación y la del agua, las dificultades en el acceso a la consulta médica y aún razones culturales que favorecen las medicinas "alternativas" son algunos de los factores responsables. También se ha postulado una disfunción inmune como parte esencial de este fenómeno. En lo que respecta a las varias anomalías inmunológicas reportadas en asociación a la malnutrición cabe hacer algunas consideraciones: Los pacientes reportados son en general moderada o severamete desnutridos y frecuentemente afectados de infecciones concomitantes. La corrección de la desnutrición, asociada a la mejoría de las variables inmunológicas, usualmente fue acompañada de tratamiento de las infecciones bacterianas y parasitarias concomitantes. Los estudios inmunológicos reportados detectan diferencias entre la población bien nutrida (controles) y los individuos malnutridos. Los efectos de la sobreexposición a niveles elevados de contaminación y de la presencia eventual de infecciones clínicas o subclínicas, parasitarias y bacterianas, frecuentemente presentes en individuos desnutridos, son difíciles de evaluar. La causa mas importante de infecciones reiteradas en niños no es la disfunción inmune sino la elevada exposición de microorganismos. Las infecciones severas pueden verse en huespedes inmunologicamente normales. Solamente las infecciones oportunistas se presentan casi exclusivamente en individuos inmunodeficientes. Las anomalías mas frecuentemente descriptas en desnutridos se sitúan en las áreas del complemento, fagocítica y de la inmunidad mediada por células. La inmunidad humoral se ha encontrado habitualmente conservada. Algunas de las anomalías inmunológicas presentes en el huésped desnutrido están probablemente ligadas a las múltiples deficiencias nutricionales presente en la malnutrición severa y representan verdaderos defectos inmunológico

Protective mucosal Th2 immune response against Toxoplasma gondii by murine mesenteric lymph node dendritic cells.

Toxoplasma gondii, an obligate intracellular parasite pathogen which initially invades the intestinal epithelium before disseminating throughout the body, may cause severe sequelae in fetuses and life-threatening neuropathy in immunocompromised patients. Immune protection is usually thought to be performed through a systemic Th1 response; considering the route of parasite entry it is important to study and characterize the local mucosal immune response to T. gondii. Despite considerable effort, Toxoplasma-targeted vaccines have proven to be elusive using conventional strategies. We report the use of mesenteric lymph node dendritic cells (MLNDCs) pulsed ex vivo with T. gondii antigens (TAg) as a novel investigation approach to vaccination against T. gondii-driven pathogenic processes. Using a murine model, we demonstrate in two genetically distinct mouse strains (C57BL/6 and CBA/J) that adoptively transferred TAg-pulsed MLNDCs elicit a mucosal Toxoplasma-specific Th2-biased immune response in vivo and confer strong protection against infection. We also observe that MLNDCs mostly traffic to the intestine where they enhance resistance by reduction in the mortality and in the number of brain cysts. Thus, ex vivo TAg-pulsed MLNDCs represent a powerful tool for the study of protective immunity to T. gondii, delivered through its natural route of entry. These findings might impact the design of vaccine strategies against other invasive microorganisms known to be delivered through digestive tract.

T cell clones from Schistosoma haematobium infected and exposed individuals lacking distinct cytokine profiles for Th1/Th2 polarisation.

T cell clones were derived from peripheral blood mononuclear cells of Schistosoma haematobium infected and uninfected individuals living in an endemic area. The clones were stimulated with S. haematobium worm and egg antigens and purified protein derivative. Attempts were made to classify the T cell clones according to production of the cytokines IL-4, IL-5 and IFN-gamma. All the T cell clones derived were observed to produce cytokines used as markers for the classification of Th1/Th2 subsets. However, the 'signature' cytokines marking each subset were produced at different levels. The classification depended on the dominating cytokine type, which was having either Th0/1 or Th0/2 subsets. The results indicated that no distinct cytokine profiles for polarisation of Th1/Th2 subsets were detected in these S. haematobium infected humans. The balance in the profiles of cytokines marking each subset were related to infection and re-infection status after treatment with praziquantel. In the present study, as judged by the changes in infection status with time, the T cell responses appeared to be less stable and more dynamic, suggesting that small quantitative changes in the balance of the cytokines response could result in either susceptibility or resistant to S. haematobium infection.

T cell clones from Schistosoma haematobium infected and exposed individuals lacking distinct cytokine profiles for Th1/Th2 polarisation

T cell clones were derived from peripheral blood mononuclear cells of Schistosoma haematobium infected and uninfected individuals living in an endemic area. The clones were stimulated with S. haematobium worm and egg antigens and purified protein derivative. Attempts were made to classify the T cell clones according to production of the cytokines IL-4, IL-5 and IFN-gamma. All the T cell clones derived were observed to produce cytokines used as markers for the classification of Th1/Th2 subsets. However, the 'signature' cytokines marking each subset were produced at different levels. The classification depended on the dominating cytokine type, which was having either Th0/1 or Th0/2 subsets. The results indicated that no distinct cytokine profiles for polarisation of Th1/Th2 subsets were detected in these S. haematobium infected humans. The balance in the profiles of cytokines marking each subset were related to infection and re-infection status after treatment with praziquantel. In the present study, as judged by the changes in infection status with time, the T cell responses appeared to be less stable and more dynamic, suggesting that small quantitative changes in the balance of the cytokines response could result in either susceptibility or resistant to S. haematobium infection

Regulatory functions of self-restricted MHC class II allopeptide-specific Th2 clones in vivo.

We studied T-cell clones generated from grafts of rejecting and tolerant animals and investigated the regulatory function of Th2 clones in vitro and in vivo. To prevent allograft rejection, we treated LEW strain recipient rats of WF strain kidney grafts with CTLA4Ig to block CD28-B7 costimulation. We then isolated epitope-specific T-cell clones from the engrafted tissue, using a donor-derived immunodominant class II MHC allopeptide presented by recipient antigen-presenting cells. Acutely rejected tissue from untreated animals yielded self-restricted, allopeptide-specific T-cell clones that produced IFN-gamma, whereas clones from tolerant animals produced IL-4 and IL-10. Adoptive transfer into naive recipients of Th1 clones, but not Th2 clones, induced alloantigen-specific delayed-type hypersensitivity (DTH) responses. In addition, Th2 clones suppressed DTH responses mediated by Th1 clones in vivo and blocked Th1 cell proliferation and IFN-gamma production in vitro. A pilot human study showed that HLA-DR allopeptide-specific T-cell clones generated from patients with chronic rejection secrete Th1 cytokines, whereas those from patients with stable graft function produce Th2 cytokines in response to donor-specific HLA-DR allopeptides. We suggest that self-restricted alloantigen-specific Th2 clones may regulate the alloimmune responses and promote long-term allograft survival and tolerance.

The Th1-Th2 classification of cellular immune responses: concepts, current thinking and applications in haematological malignancy.

The finding that T cell immune responses could be divided into those promoting cell mediated immunity (Th1) and humoral responses (Th2) has had a profound effect on the understanding of immune response generation over the last 15 years. With ever increasing knowledge of the immune system, the model has come under criticism, as not all responses easily fit the classification. Nonetheless, the model still provides a valuable framework on which to base immunological research. In this review we update the model with current thinking regarding the generation and maintenance of immune responses. We then examine how the Th1-Th2 paradigm may be applied in developing new understanding of several topical issues in haematological malignancy-control of graft-versus-host disease; cytokine control of proliferating clones in B and T cell diseases; and suppression of T cell responses in multiple myeloma.

Nasal immune system: distinctive Th0 and Th1/Th2 type environments in murine nasal-associated lymphoid tissues and nasal passage, respectively.

The nasal mucosa, an important arm of the mucosal immune system, is the first site of contact with inhaled antigens to induce an IgA response. A major aim of this study was to characterize the Th1 and Th2 cytokine expression of mucosal T cells residing in nasal-associated lymphoid tissue (NALT) and nasal passages (NP) as IgA inductive and effector sites, respectively, at the transcription and cellular levels. An application of single-cell reverse transcription-PCR for analysis of Th1 (IFN-gamma) and Th2 (IL-4 and IL-6) cytokine-specific mRNA revealed the presence of CD4+ T cells with a Th0 profile in NALT, while high numbers of Th2 cytokine-specific mRNA expressed by CD4+ T cells were noted in NP followed by Th1-type cells. NALT CD3+ CD4+ T cells of Th0 type have the capacity to become Th1- and/or Th2-type cells since their activation via the TCR-CD3 complex resulted in the expression of an array of Th1 and Th2 cytokines. CD3+ CD4+ T cells from NP, but not NALT, provide a helper function for the induction of antibody-forming cells including IgA isotype in B cell cultures. These findings suggest that NALT is characterized by a Th0 environment which can gain a Th1 and/or Th2 phenotype. In contrast, NP is considered to be a Th2 dominant site with some Th1 cells that can support the induction of IgA-producing cells.

Th1 and Th2 CD4+ cells in the pathogenesis of allergic diseases.

Our understanding of the molecular and genetic etiologies of allergic disorders, which affect 20%-30% of the general population, has greatly improved over the past several years. Previously, research focused on examination of immediate hypersensitivity reactions, initiated by the cross-linking of IgE molecules on the surface of mast cells/basophils, resulting in the release of a host of mediators, which cause symptoms typified by acute anaphylaxis. Although there has been substantial progress in understanding the molecular biology of mast cell and basophil activation and of the regulation of IgE synthesis, recent studies have shifted attention to the cellular and molecular mechanisms that cause a broader allergic inflammatory response and underlie the more chronic and severe symptoms of allergy and asthma. In this report, we will review a substantial body of recent experimental work that has provided the basis for our new understanding of the allergic inflammatory response and the pathogenesis of allergic diseases. We will describe the recent progress in defining the immunological basis for allergic disease, and how subsets of helper CD4+ T cells secreting a specific array of cytokines (Th2 cytokines) regulate/cause allergic inflammation. We will review the cell biology of Th2 cells, the role of Th2 cells in allergic disease, and biological, genetic, and therapeutic mechanisms that influence the differentiation of CD4+ T cells and enhance or suppress cytokine synthesis in Th2 cells. These mechanisms control the expression of allergic diseases, which occur in some but not all individuals following environmental exposure to allergens.

Co-stimulation-induced release of pro-inflammatory cytokine interleukin-8 by allergen-specific T cells.

Chemokines, which include interleukin (IL)-8, are a family of pro-inflammatory molecules with potent chemoattractant activity on neutrophils, as well as other cell types. IL-8 can be recovered from many inflammatory sites. To test the hypothesis that Th2-type allergen-specific T cells, known to be the main cell type governing the allergic inflammation, are a source of IL-8 and to investigate whether IL-8 release is influenced by the nature of the in vitro mitogenic or co-mitogenic stimulation, cypress-specific T-cell clones (TCC) were generated from five allergic subjects during in vitro seasonal exposure to the allergen. Purified cypress extract was produced directly from freshly collected pollen and used for in vitro stimulation of PBMC bulk cultures. After 5 days priming and a further 7 day period of IL-2-driven cell expansion, monoclonal antibodies to CD3, CD2 and CD28 were adopted for in vitro restimulation of allergen-specific cell lines or, subsequently, secondary established TCC. The induction of apoptosis was detected by propidium iodide (PI) cytofluorimetric assay. Basal and co-stimulation-induced IL-8 production was measured by an ELISA method. Both cypress-specific T-cell lines and TCC secreted appreciable amounts of IL-8. By cross-linking T-cell lines or Th2 CD4+ TCC with CD3, CD2 or CD28 MoAbs, the authors observed a great stimulation-induced IL-8 secretion, preferentially after CD2 or combined CD2/CD28 stimulation. In addition, CD4+ clones released large amounts of IL-8 into culture supernatants after CD2 stimulation while undergoing programmed cell death (30-40% hypodiploid DNA profile of PI-stained cells). In contrast, CD3 crosslinking was unable to determine the release of IL-8 or the induction of apoptosis. Taken together, these results suggest that incomplete TcR engagement by allergen may lead to the secretion of pro-inflammatory cytokines with a contemporary induction of apoptosis in a significant number of target cells. This phenomenon may represent an additional way for local recruitment of neutrophils and basophils.

TCRV beta 7+ Th2 cells mediate UVB-induced suppression of murine contact photosensitivity by releasing IL-10.

In murine contact photosensitivity, a cutaneous delayed-type hypersensitivity reaction, preirradiation of the photosensitization site with UVB induced Ag-specific, afferent limb-acting, CD4+CD8- suppressor T cells (Ts). The present study examined usage of TCR V beta and production of immunosuppressive cytokines in Ts propagated in vitro. Spleen cells from UVB-preirradiated, 3,3',4',5- tetracholorosalicylanilide (TCSA)-photosensitized mice were stimulated with 3000-rad-irradiated lymph node cells (LNC) from TCSA/UVA-sensitized mice (LNCTCSA) in the presence of rIL-t. After several rounds of antigenic stimulation, a T cell line (B+TCL) consisted exclusively of CD3+CD4+CD8- V beta 7+ and V beta 13+ populations. Transfer to naive recipients of B+TCL treated with anti-V beta mAb plus complement revealed that the V beta 7+ cells suppressed both the in vivo and the in vitro aspects of contact photosensitivity to TCSA in an Ag-specific manner. The in vitro suppressive activity of B+TCL was neutralized by anti-IL-10 mAb, but not by anti-IL-4 mAb, indicating a crucial role of IL-10 in UBV-induced suppression. Upon stimulation with 3000-rad-irradiated-LNCTCSA, B+TCL released IL-4 and IL-10 but not IL-2, and V beta 7+ cells produced IL-10. The reverse transcriptase-PCR detected mRNA for IL-4 and IL-10 but not that for IL-2, IFN-gamma, or TGF-beta in B+TCL stimulated with or without concanavalin A. In accordance with the findings in B+TCL, spleen cells from UVB preirradiation plus TCSA/UVA mice contained V beta 7+ T cells that suppressed contact photosensitivity to TCSA and produced substantial amounts of IL-4 that provided a microenvironment for Th2 cell generation. We conclude that UVB preirradiation and photosensitization result in the generation of V beta 7+ Th2 cells that suppress contact photosensitivity by releasing IL-10. The dysfunction of effector Th1 cells underlying UVB suppression of delayed-type hypersensitivity seems to be due not only to altered APC function but also to counteraction of Th2 cells by Th1 cells.

The ontogeny of class-regulation of CD4+ T lymphocyte populations.

The differential class-regulation of CD4+ T lymphocyte populations is believed to play a major role in determining the qualitative behaviour of the immune system, and in the fate of immune responses in particular. In this article we propose a model for the dynamics of the Th1 and Th2 subpopulations. We put forward the concept of an 'antigenic niche' which allows us to postulate that the key feature underlying the regulation of Th differentiation pathways is the population dynamics of the lymphocytes themselves. Using this model we are able to account for a number of well established experimental observations which were hitherto apparently unrelated and poorly understood. This suggests that our simplified model might be capturing some essential features of the immune system.