Development Of Bronchus-associated Lymphoid Tissue Research Articles

The bronchus-associated-lymphoid tissue (BALT) an unique lymphoid organ in man and animals

The development structure and number of bronchus-associated lymphoid tissue (BALT) will be described in many different animals (like chicken, rabbit, mouse, rat, farm animals and particular the pig, monkey) and these data compared to healthy man and in human diseases. The term induced BALT should not be used because it is a tertiary lymphoid structure, which lacks the contact to a bronchus and does not consist of the important area (dome area) which is essential for antigen uptake of microbial stimuli, which are essential in the development of BALT. Mycoplasma seems to play a critical role as shown in pigs but there not been documented in other species like rabbits. More studies have to be performed in health and disease (e.g. in apes) to document the structural and functional basis to use BALT as an entry site for vaccination protocols.

Induction and Analysis of Bronchus-Associated Lymphoid Tissue.

Bronchus-associated lymphoid tissue (BALT) forms spontaneously in the lung after pulmonary infection and has been identified as a highly organized lymphoid structure supporting the efficient priming of T cells in the lung. To explore the mechanisms and instructive signals controlling BALT neogenesis we used both, a single dose of vaccinia virus MVA and repeated inhalations of heat-inactivated Pseudomonas aeruginosa (P. aeruginosa). Intranasal administration of both pathogens induces highly organized BALT but distinct pathways and molecules are used to promote the development of BALT. Here, we describe the induction and phenotype of the distinct types of BALT as well as the immunofluorescence microscopy-based analysis of the induced lymphoid tissue in the lung.

Tertiary Lymphoid Structures Target the Antitumor Immune Response to Lung Cancer

Tertiary Lymphoid Structures Target the Antitumor Immune Response to Lung Cancer

Autoreactive T and B Cells Induce the Development of Bronchus-Associated Lymphoid Tissue in the Lung

Rheumatoid arthritis-related interstitial lung disease (RA-ILD) is associated with significant morbidity and mortality. Studies in humans have found that the incidence of bronchus-associated lymphoid tissue (BALT) correlates with the severity of lung injury. However, the mechanisms underlying the development of BALT during systemic autoimmunity remain unknown. We have determined whether systemic autoimmunity in a murine model of autoimmune arthritis can promote the development of BALT by generating a novel murine model derived from K/BxN mice. Transgenic mice with the KRN T-cell receptor specific for the autoantigen, glucose-6-phosphate isomerase (GPI), were crossed with GPI-specific immunoglobulin heavy and light chain knock-in mice, producing mice with a majority of T and B cells specific for the same autoantigen. We found that 67% of these mice demonstrated lymphocytic infiltration in the lungs, localized to either the perivascular or peribronchial regions. Fifty percent of the mice with lymphocytic infiltration manifested lymphoid-like lesions resembling BALT, with distinct T and B cell follicles. The lungs from mice with lymphoid infiltrates had increased numbers of cytokine-producing T cells, including IL-17A(+) T cells and increased major histocompatibility complex Class II expression on B cells. Interestingly, challenge with bleomycin failed to elicit a significant fibrotic response, compared with wild-type control mice. Our data suggest that systemic autoreactivity promotes ectopic lymphoid tissue development in the lung through the cooperation of autoreactive T and B cells. However, these BALT-like lesions may not be sufficient to promote fibrotic lung disease at steady state or after inflammatory challenge.

Expression of TNF‐α, IFN‐γ, TGF‐β and IL‐7 on cells isolated from the Bronchoalveolar Fluid in a model of secondary immunodeficiency.

We have previously reported the early appearance (4 days post partum) of γδT cells that colocalize with TNF‐α in Bronchus‐Associated Lymphoid Tissue (BALT), indicating the important role of this cytokine for BALT development. In our experimental model of secondary immunodeficiency due to severe protein deprivation at weaning followed by administration of a 20% casein diet during 21 days (R21), we also demonstrated an increase of TCR γδ+ cells accompanied by an increase in TNF‐α+ cells number in R21. The objective of this work is to analyze and compare cells isolated from the bronchoalveolar fluid (BAL) in R21 vs control rats: 1) the expression of TNF‐α and IFN‐γ, as indicator of an inflammatory process and its regulation by TGF‐β and 2) the cellular regulation by IL‐7. Western Blot analysis showed an increase of all cytokines in cells from BAL of R21 animals when compared to control rats (Figure 1). Our results indicate the existence of an inflammatory process (due to TNF‐α and IFN‐γ) modulated by TGF‐β. The increment of IL‐7 correlates with its capacity for the proliferation and differentiation of γδ T cells, which are increased in BAL from R21 as previously reported. Moreover, we suggest a protective role of IL‐7 in the inflammatory focus.Supported by B010 grant.

Regulatory T cells interfere with the development of bronchus-associated lymphoid tissue

Presence and extent of bronchus-associated lymphoid tissue (BALT) is subject to considerable variations between species and is only occasionally observed in lungs of mice. Here we demonstrate that mice deficient for the chemokine receptor CCR7 regularly develop highly organized BALT. These structures were not present at birth but were detectable from day 5 onwards. Analyzing CCR7−/−/wild-type bone marrow chimeras, we demonstrate that the development of BALT is caused by alterations of the hematopoietic system in CCR7-deficient mice. These observations together with the finding that CCR7-deficient mice posses dramatically reduced numbers of regulatory T cells (T reg cells) in the lung-draining bronchial lymph node suggest that BALT formation might be caused by disabled in situ function of T reg cells. Indeed, although adoptive transfer of wild-type T reg cells to CCR7-deficient recipients resulted in a profound reduction of BALT formation, neither naive wild-type T cells nor T reg cells from CCR7−/− donors impair BALT generation. Furthermore, we provide evidence that CCR7-deficient T reg cells, although strongly impaired in homing to peripheral lymph nodes, are fully effective in vitro. Thus our data reveal a CCR7-dependent homing of T reg cells to peripheral lymph nodes in conjunction with a role for these cells in controlling BALT formation.

A precious experience of lobar transplantation in a teenager with end-stage chronic hypersensitivity pneumonia: Case report

Pulmonary fibrosis inevitably develops in patients with chronic hypersensitivity pneumonia (CHP). Lobar transplantation may be a viable option for pediatric and small adult patients with end-stage CHP and life-threatening respiratory decompensation. We describe a 16-year-old girl experiencing end-stage pigeon breeder's hypersensitivity pneumonia with right heart failure, who received left allograft lobar transplantation and had an uneventful convalescent course for 1 year after transplantation. Histopathologically the excised native lung revealed diffuse infiltration of lung parenchyma by CD3 + and CD8 + cells with an absence of CD4 + cells, whereas T-lymphocyte subsets analysis revealed no abnormalities in the blood. This finding is consistent with the contribution of a local type IV immune reaction to the pathogenesis. In addition, the observation of specific cellular distribution of bronchus-associated lymphoid tissue suggests that chronic antigenic stimulation and /or inflammation in CHP may cause bronchus-associated lymphoid tissue development, which is likely to play an important role in the mucosal immune response of this disease.

INHALATION OF DIESEL EXHAUST FOR THREE MONTHS AFFECTS MAJOR CYTOKINE EXPRESSION AND INDUCES BRONCHUS-ASSOCIATED LYMPHOID TISSUE FORMATION IN MURINE LUNGS

The authors investigated the effects of exposure to diesel exhaust (DE) on murine lung tissues invivo. BALB/c and C57BL/6 mice were exposed to DE with low (100 μ g/m 3) and high (3 mg/m 3) DE particle levels for 3 months. The authors then examined morphological changes and the expression of mRNAs for various cytokines (tumor necrosis factor [TNF]- α, interleukin [IL]-1 β, IL-4, IL-6, IL-10, IL-12p40, and interferon [IFN]- γ) and inducible nitric oxide synthase (iNOS) in the lungs, as well as TNF- α, IL-1 β, IL-10, IL-12p40, and Mac-1 mRNA expression in alveolar macrophages (AMs). TNF- α, IL-12p40, IL-4, and IL-10 mRNA expression were mildly increased, whereas IL-1 β mRNA and iNOS expression were slightly decreased, in the low- and high-level exposure groups. Flow cytometry of bronchoalveolar lavage fluid revealed a significant increase in Mac-1-positive cells in the high-level exposure group. On histological examination, bronchus-associated lymphoid tissue (BALT), containing B and T lymphocytes, had developed only in the high-level exposure group. Chronic inhalation of DE influences cytokine expression in the murine lung, and induces phagocytosis and BALT development. These findings suggest that DE may provoke immunological responses by acting as a foreign body in the lung, and that even low-level exposure may induce allergic reactions.

Ex vivo development of functional human lymph node and bronchus-associated lymphoid tissue

We introduce a novel in vivo model of human mucosal immunity, based on the implantation of human fetal bronchial mucosa and autologous peribronchial lymph node (PLN) in the severe combined immunodeficiency (SCID) mouse. In the SCID host, human fetal bronchi implanted alone retain macrophages and mast cells but lose T cells. In contrast, fetal bronchi co-implanted with PLN contain, in addition to macrophages and mast cells, numerous T cells and B cells, often clustered in intramucosal bronchus-associated lymphoid tissue (BALT). Functionally, bronchus-PLN cografts are able to mount robust alphabeta and gammadelta T-cell-mediated immune responses to Pseudomonas aeruginosa and 3,4-epoxy-3-methyl-1-butyl-diphosphate challenges. No other autologous lymphoid organ (bone marrow, thymus, liver) allows for BALT development in co-implanted bronchi, which suggests special ontogenetic and functional relations between extramucosal PLN and intramucosal BALT. Overall, the bronchus-PLN cograft appears as a promising model for human bronchial immune development and function. Our study is the first to document long-term ex vivo maintenance of functional human lymph nodes as native appendices to mucosal tissue. Our results, therefore, suggest a simple strategy for developing similar experimental models of human immune function in other mucosae.

Migratory patterns of thoracic duct lymphocytes into bronchus-associated lymphoid tissue of immunized rats.

Lymphocytes continuously circulate between the bloodstream and lymphoid organs, and their migration into lymphatic tissues presumably occurs through selective mechanisms. Although bronchus-associated lymphoid tissue (BALT) is known as an inductive tissue of the common mucosal immune system, little is known about how effectively the lymphocytes in the blood vessels migrate into the BALT, thereby enabling the BALT to act as an effector tissue in the immunologic responses of the lungs. To analyze whether or not thoracic duct lymphocytes (TDL) from immunized and nonimmunized rats possess different migratory patterns to the BALT, 5-(6)-carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled TDL were injected into rats with BALT hyperplasia that was produced by intratracheal administration of TNP-KLH, and then the number of labeled cells in the BALT were examined by immunohistochemical methods. We studied the following three groups at 12 h after the injection: group A, intraintestinally immunized donors and intratracheally immunized recipients; group B, nonimmunized donors and intratracheally immunized recipients; group C (control group), nonimmunized donors and nonimmunized recipients. Time course studies 0.5, 4, 12, and 24 h after the injection were done in groups A and C. In a cytokinetic study, larger numbers of CFSE-labeled lymphocytes were found at 12 h and 24 h in group A than in group C. At 12 h after the injection, the absolute number of CFSE-labeled lymphocytes per BALT was significantly higher in group A than in group B (p < 0.05), and was lowest in group C. Histologically, there was a marked proliferation of high endothelial venules (HEV), with findings of adhesion and influx of lymphocytes inside the HEV in group A. These observations indicate that the immunized BALT actively recruits immunized TDL through a specific mechanism of lymphocyte-endothelium recognition in HEV, which partially explains the process of BALT development as an effector tissue for local immunity.

Antigen uptake and subsequent cell kinetics in bronchus-associated lymphoid tissue.

Bronchus-associated lymphoid tissue (BALT) plays an important role in the immunological defence of airways. However, the mechanisms of BALT development, antigen sampling, and subsequent cell kinetics remain unclear. To clarify these chronological processes, we used a Pseudomonas aeruginosa-exposed mouse model. In BALB/c and C57BL/6 mice, BALT development was induced by inhalation of heat-killed P. aeruginosa after sensitization with subcutaneous injection of P. aeruginosa in the presence of Freund's complete adjuvant. Subsequently, we chronologically killed these mice who had inhaled PKH26-labelled P. aeruginosa and examined bacterial transport using fluorescence microscopy. The distribution of interleukin-4-positive cells and interferon-gamma-positive cells was studied immunohistochemically. The degree of BALT hyperplasia was greater in sensitized mice than in non-sensitized mice and in BALB/c mice than in C57BL/6 mice. PKH26-labelled bacteria were found in BALT earlier in sensitized mice than in non-sensitized mice. Immunohistochemical studies revealed that interleukin-4-positive cells predominated over interferon-gamma-positive cells in the peripheral areas of lymphoid follicles. These results indicate that administered antigens are actively transported into BALT and that sensitized Th2 lymphocytes play an important role in forming and maintaining BALT.

Development of Bronchus-Associated Lymphoid Tissue in Chronic Hypersensitivity Pneumonitis

Bronchus-associated lymphoid tissue (BALT) is well defined in animals. In humans, however, BALT has been reported to be inducible under pathologic conditions, such as chronic respiratory infection, although it is not present in healthy adults. Thus, induced BALT is considered to be involved in the mucosal immunity of the human lung under these conditions. However, there have been few studies to investigate BALT development in hypersensitivity pneumonitis. The aim of this study was to examine the presence of BALT in hypersensitivity pneumonitis, especially in its chronic form. The subjects included five patients with chronic hypersensitivity pneumonitis (CHP) diagnosed from clinical and histologic findings. We investigated histologically the development of BALT in these patients. Further, the cellular distribution of BALT was also examined by immunohistochemistry. BALT was present in three of five patients with CHP. Immunohistochemical examination revealed the follicular area of BALT to be composed mainly of B cells, while the parafollicular area comprised predominantly T cells. Centroblasts located in the germinal center of BALT expressed Ki-67 antigen, a marker of cell proliferation, suggesting that these cells were actively proliferating after antigenic stimulation. Cells expressing bcl-2, which is present primarily on memory B cells, were confined to the follicular area, devoid of any germinal centers. S-100-positive, CD1a-negative interdigitating dendritic cells were observed in the dome area of BALT. These observations suggest that chronic antigenic stimulation and/or inflammation in CHP may cause BALT development, which, in turn, is likely to play an important role in the mucosal immune response of this disease.

Cellular distribution of bronchus-associated lymphoid tissue in rheumatoid arthritis.

Bronchus-associated Lymphoid tissue (BALT) has been reported to be present in the lungs of patients with rheumatoid arthritis (RA). However, little is known about the structure and cellular distribution of BALT in this disease, so we investigated these points using immunohistochemical methods. The subjects were eight RA patients with BALT in biopsy specimens and a histologic diagnosis of follicular bronchiolitis. Seven patients had cough and purulent sputum, and four patients had positive sputum cultures. BALT was histologically composed of four distinct regions, which were the lymphoepithelium, the dome area, the follicular area, and the parafollicular area. Surface IgM+ B cells were predominant in the follicular area, whereas IgA+ cells were scattered in the dome and parafollicular areas. T cells were mainly found in the parafollicular area (CD4+ > CD8+), and most of them expressed the T Cell receptor alpha beta (alpha beta TCR). These findings were similar to those described previously for BALT in diffuse panbronchiolitis, which manifests as a chronic respiratory infection. The present study indicated that extrinsic stimulation as well as alterations of the immune response are involved in the development of BALT in RA, although the exact mechanism requires further clarification.

Development of bronchus-associated lymphoid tissue in goats.

Development of bronchus-associated lymphoid tissue (BALT) was studied in clinically healthy and diseased Assam local goats. Animals were sacrificed before term as well as at different postnatal periods to screen lung sections for the presence of BALT. In a retrospective study sections prepared from pneumonic lungs were examined for any alteration of BALT. No BALT-like structure was found in neonatal goats. Bronchial lymphoid structures appeared in half of the animals from 1 month of age onward. The frequency of the BALT/4.5 cm2 of lung section ranged from one to two in 1-month-old and three to six in 1-year-old goats. In pneumonic lungs BALT became hyperplastic, and the size was also increased. The incidence of BALT was increased in lungs with fibrotic pneumonia. The number of BALT/section was high (five to eight/4.5-cm2 area) in mesenchymal cell proliferation. The present study shows that BALT did not develop in prenatal periods. But in the presence of potent antigens lymphoid aggregates appeared in the bronchial lamina propria of normal and diseased lungs.

Structure and Development of Bronchus-Associated Lymphoid Tissue in Conventionally Reared Broiler Chickens

The development of bronchus-associated lymphoid tissue (BALT) in conventionally reared broiler chickens of 1 day and 1, 2, 3, 4, 6, and 8 weeks of age was studied using light and electron microscopy (scanning and transmission). BALT in these chickens resembled other mucosa-associated lymphoid tissues (MALT) in that it was composed of an altered epithelium overlying a population of lymphocytes and contained potential antigen-presenting cells, such as macrophages and dendritic cells; high endothelial venules were also present. In contrast to other MALT, epithelial cells in chicken BALT were not of the M-cell type; i.e., they lacked large numbers of apical tubules and vesicles for specialized uptake of luminal antigens. There were age-related differences in size, number, and cellular composition of BALT nodules. Lymphoid nodules were progressively larger and more numerous with increasing age. Germinal centers were present in birds 2 weeks of age and older. BALT epithelium was primarily squamous and non-ciliated in 1-day and 1-week-old chicks, becoming progressively more columnar and ciliated in older chickens. Lymphocyte infiltration of the epithelium was extensive at 1 to 4 weeks of age; in older chickens, distinct epithelial and lymphocytic compartments were separated by connective tissue.

Ontogenic study on the bronchus-associated lymphoid tissue (BALT) in the rat, with special reference to dendritic cells.

In several mammalian species, the bronchus-associated lymphoid tissue (BALT) appears as condensed lymphoid aggregates to the bronchial wall. Recently, a population of antigen-bearing cells with dendritic morphology has been identified in rat respiratory tract tissue (Sertl et al., 1986). We studied on the ontogenic development of BALT with special reference to dendritic cells (DC) of rat lung ultrastructurally and immunohistochemically.KeywordsDendritic CellFollicular Dendritic CellMajor Histocompatibility Complex AntigenNational Defense Medical CollegeOntogenic Development

Low incidence of bronchus-associated lymphoid tissue (BALT) in chronically inflamed human lungs.

The relevance of bronchus-associated lymphoid tissue (BALT) in man is still under discussion. Animal experiments indicate that the development of BALT is dependent on microbial stimulation. Therefore, the incidence of BALT was investigated retrospectively in specimens removed during surgical procedures on patients with chronic pulmonary inflammation. All these patients had severe chronic bronchitis and bronchiectasis, but BALT was found in only 8%. In patients with BALT and a malignant tumor, occlusion of a bronchus with poststenotic pneumonia was always present and BALT was observed exclusively in areas peripheral to the occlusion. In man other compartments of the lung must be responsible for the immune function of BALT found in animals.

Ultrastructural and immunohistochemical studies on the ontogenic development of bronchus-associated lymphoid tissue (BALT) in the rat: special reference to follicular dendritic cells

The ontogenic development of lymphoid and non-lymphoid cells in bronchus-associated lymphoid tissue (BALT) of the rat was studied ultrastructurally and immunohistochemically. In the late foetal period, only the alveolar macrophages showed a weak positivity for leucocyte common antigen, but no immune region associated (Ia) antigen was detected by monoclonal antibody, MAS 043. Mast cells were present. At 6 days of age, Ia-positive cells were observed in the alveolar wall and peribronchial interstitial tissue, and ultrastructurally there was an aggregation of the fibroblastoid mesenchymal cells. By 10 days of age, the aggregation of lymphoid cells together with S-100-positive reticulum cells had formed a BALT-like periarterial lymphoid sheath. In the adult animals, an obvious B-cell area was present in the central part and subepithelium of BALT, whilst in this area, S-100-positive, strongly Ia-positive cells with a dendritic form were observed. These dendritic cells appeared to be identical to the follicular dendritic cells (FDC) seen in the secondary follicles of lymphoid organs. Those cells may be derived from the fibroblastic reticulum cells, and may function to present antigen to lymphocytes.

Postnatal Development of Bronchus-Associated Lymphoid Tissue (Balt) in the Rat, Rattus Norvegicus

The pattern of development of bronchus-associated lymphoid tissue (BALT) in specified-pathogen-free and conventional (non-barrier maintained) rats over the initial 4 weeks of life appeared to be similar. BALT first appeared around the 2nd week of life and increased in amount over the following 2 weeks. Overlying large nodules of BALT the bronchial epithelium becomes infiltrated by lymphocytes to form a lymphoepithelium. This transformation occurs earlier in conventional rats, possibly because of the differing antigen levels to which they are exposed.