Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Lymphoid Tissue”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

Distribution of catecholaminergic neurotransmitters and related receptors in human bronchus-associated lymphoid tissue.

BACKGROUND: The functions of the bronchus-associated lymphoid tissue (BALT) are under the control of the autonomic nervous system (sympathetic and parasympathetic nerve fibers). OBJECTIVES: The relationships between the adrenergic nerve fibers and beta-adrenergic receptors were studied in the human BALT with the aim to demonstrate a probable neuromodulation. METHODS: Morphological observations (staining with hematoxylin-eosin and scanning electron microscopy images) were carried out on samples of human BALT harvested during autopsies. Moreover, histochemical staining for norepinephrine (adrenaline = adrenergic nerve fibers) as well as for other catecholamines was performed. Finally, beta-adrenergic receptors were stained by means of a beta-blocking, radiolabeled drug (pindolol 125I). All our data were submitted to morphometric analysis (quantitative analysis of images and statistical analysis of data). RESULTS: Our results provide direct evidence of the presence and distribution of catecholaminergic nerve fibers and related beta-adrenergic receptors in BALT. beta-Adrenergic receptors are present above all in the most richly innervated part of the BALT, and are, therefore, in close relationship with their related adrenergic nerve fibers. CONCLUSIONS: Studies on the distribution of adrenergic neurotransmitters and related beta-adrenergic receptors in the human BALT are the first step for the demonstration of a probable neuromodulation of BALT.

Adrenergic Fibers↗
PubMed2005

Cholinergic staining of bronchus- associated lymphoid tissue.

The cholinergic staining of human bronchus-associated lymphoid tissue (BALT) was studied in humans. Morsels of the human lung (containing BALT) were harvested, after having obtained the appropriate approvals, during autopsies in 24 human subjects. The samples were stained by means of the enzymatic technique of acetylcholinesterase (AChE) and/or the monoclonal immunohistochemical method of choline acetyltransferase (ChAT). A morphometrical analysis was performed by means of quantitative analysis of images and statistical analyses of the data. AChE and proteins were also measured by biochemical assay. Our results demonstrate that both AChE and ChAT are localized in the BALT of young and old humans. These enzymes undergo age-related changes. The biochemical values of AChE are as follows: 22.3 +/- 2.5 international units in young subjects and 78.5 +/- 1.9 international units in old ones. The morphometrical values of AChE confirm the biochemical ones. The morphometrical data for ChAT are 31.6 +/- 1.4 conventional units in young subjects and 71.2 +/- 1.5 conventional units in old ones. Further results are needed to draw definite conclusions concerning the location and the distribution of these two enzymatic activities in BALT. In our opinion, the presence of AChE and ChAT in BALT can be both 'non-neuronal', with a role in general metabolism, and/or 'neuronal' with a role in neuroimmunomodulation.

Acetylcholine↗
PubMed1997

Endoscopic ultrasonography for the initial staging and follow-up in patients with low-grade gastric lymphoma of mucosa-associated lymphoid tissue treated medically.

BACKGROUND: Endoscopic ultrasonography is an appropriate procedure to assess the depth of tumoral infiltration in primary gastric lymphoma. The aims of the present study were to characterize the endoscopic ultrasonographic aspects of low-grade gastric lymphoma of mucosa-associated lymphoid tissue and to determine the value of this procedure in medical treatment assessment. METHODS: Between 1991 and 1996, 15 patients with low-grade gastric lymphoma of mucosa-associated lymphoid tissue were treated with oral cyclophosphamide and/or anti-Helicobacter pylori treatment. Endoscopic ultrasonography was carried out at the time of the diagnosis in all patients, 8 of whom (4 in complete remission and 4 with a stable or progressive disease) had at least one endoscopic ultrasonography examination within the treatment period (median follow-up 17 months). RESULTS: The initial procedure showed an increased gastric wall thickness from 6 to 12 mm in 8 patients, equal to 5 mm in 5 patients, and normal in 2 patients. The thickening was predominantly of the mucosa alone and/or the submucosa but never extended beyond the muscularis propria. No lymph node was found. Gastric wall thickness returned to normal in the 4 patients in complete remission and remained thick in 3 of the 4 patients with a stable or progressive disease. Of these 3 patients, at least one set of biopsy samples, carried out during follow-up, showed the absence of lymphoma, but histology performed subsequently found evidence of disease. CONCLUSIONS: Endoscopic ultrasonography differentiates superficial from infiltrative types of gastric lymphoma of mucosa-associated lymphoid tissue, which may have a prognostic significance and confirms remission or persistence of the disease with medical treatment during follow-up. When the gastric wall remains thick, even if histology is negative, repeated biopsies should be performed to detect evolving disease or relapse.

Adult↗
PubMed1990

Phenotypically distinct subpopulations of T cells in domes and M-cell pockets of rabbit gut-associated lymphoid tissues.

Follicle epithelium and domes of gut-associated lymphoid tissue (GALT) contain populations of lymphocytes which first contact antigen taken up from the intestine. In order to study the association of lymphocytes with M cells in follicle epithelium, monoclonal antibodies (mAb) were generated by immunizing BALB/c mice with lymphocytes populating GALT domes from NZW rabbits, and their specificity was assessed by immunohistochemistry and flow cytometry. mAb 3C10 (IgM) and 3B6 (IgG3) recognized subpopulations of intraepithelial lymphocytes associated with M cells. mAb 3C10 also identified macrophage-lymphocyte clusters in domes and tangible body macrophages in germinal centres of GALT but did not react with cells in T-dependent areas (TDA) or B cells in follicles. mAb 3B6 recognized lymphocytes in domes and B cells in follicles but not T cells in TDA of GALT. The distribution of 3B6+ cells overlapped with, but was more restricted than, that of Ia+ cells. Analysis of lymphocytes in follicle epithelium showed that greater than 95% of lymphocytes associated with M cells were Ia+. T cells represented approximately 95% of intraepithelial lymphocytes in the appendix and approximately 65% in Peyer's patches. A majority of intraepithelial lymphocytes was recognized by mAb 3B6, but mAb 3C10 identified only approximately 30%. Because neither 3C10 nor 3B6 recognized lymphocytes in TDA of GALT, these results indicate that most lymphocytes associated with M cells are a distinct phenotype of Ia+ T cells.

Animals↗
PubMed1993

Epitheliotropism in high-grade lymphomas of mucosa-associated lymphoid tissue.

Low-grade lymphomas of mucosa-associated lymphoid tissue (MALT) characteristically show centrocyte-like cells, plasmacytic differentiation, follicular colonization and lymphoepithelial lesions (epitheliotropism). High-grade lymphomas of MALT are thought to lack these features and can only be identified as MALT lymphomas with confidence if they are admixed with residual low-grade tumours. We studied 23 cases of MALT lymphoma of the thyroid. Six were predominantly low-grade, 12 were predominantly high-grade, and five contained both low- and high-grade areas. All cases were stained for cytokeratin, epithelial membrane antigen and laminin using an immunoperoxidase technique. The low-grade lymphomas all contained lymphoepithelial lesions, generally in the form of clusters of intra-acinar centrocyte-like cells. Eleven of the 12 high-grade MALT lymphomas of the thyroid also showed lymphoepithelial lesions. These appeared in three forms: follicles or clusters of epithelial cells infiltrated by groups of centrocyte-like cells, intra-acinar clusters of blast cells, or irregular invasion of islands of epithelial cells by blast cells. The first pattern presumably represented residual low-grade tumour over-run by high-grade lymphoma. The second two patterns indicated that the factors that result in epitheliotropism in low-grade MALT lymphomas are also present in high-grade tumours. Following this study we identified epitheliotropism in single examples of high-grade MALT lymphomas of the bronchus and small intestine. Previous failure to recognize epitheliotropism in high-grade MALT lymphomas of the gastrointestinal tract may be due to loss of the affected epithelium. The localization and relatively good prognosis of high-grade MALT lymphomas may be related to retention of MALT characteristics including epitheliotropism.

Epithelium↗
PubMed1984

Lymphoid antigenic determinants of the chicken: ontogeny of bursa-dependent lymphoid tissue.

The ontogenic development of the bursa-dependent lymphoid tissue in the chicken has been studied using rabbit antisera specific for B lymphocyte sub-populations and two elements of the bursal microenvironment. The antigens investigated were: the chicken B lymphocyte antigen ( CBLA ); mature B lymphocyte antigen ( CMBLA ); a foetal-associated antigen ( CFAA ) present on embryonic haemopoietic cells and adult bone marrow and bursa cells; immunoglobulin (Ig) and IgG; a bursa-specific cortical reticulin fibre antigen ( CBRFA ); a gut-associated mucin antigen ( CGAMA ) present on bursal medullary reticular epithelial (REp) cells. The development of suspected precursor cells was examined using a rabbit antiserum specific for foetal spleen cells. The major finding was the interrelationship between developing B cells and the bursal microenvironment. The first CBLA - and CFAA -positive cells were detected in the bursa at day 8 of incubation but their precise localization was difficult to assess. In 12-15 day embryos, both these cells were found predominantly in the tunica-propria in close proximity to cells bearing the reticulin fibre antigen CBRFA . This close association between CBLA -, CFAA - and CBRFA determinants represents the earliest stages of B cell differentiation and mimics that found in the adult bursa cortex. By day 18, the majority of bursa cells expressed CBLA and Ig and were localized in the developing medullary follicles, the REp cells of which were CGAMA -positive, demonstrating a very early interaction between intestinal tract contents, bursal REp cells and B cell maturation. Around hatching some bursa cells showed a marked increase in the membrane expression of CBLA and Ig, and the simultaneous expression of CMBLA and IgG. These cells were present in medullary follicles; CBRFA was present on cortical reticulin fibres which provided a supporting framework for the more immature CFAA -positive cells.

Animals↗
PubMed1997

Deletion of Epstein-Barr virus latent membrane protein 1 gene in United States and Brazilian Hodgkin's disease and reactive lymphoid tissue: high frequency of a 30-bp deletion.

A 30-basepair (bp) deletion in the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) gene has been reported in nasopharyngeal carcinoma and EBV-associated malignant lymphomas. Prior studies have found the deletion in about 10% to 28% of cases of Hodgkin's disease (HD), particularly in cases with aggressive histology. We studied the prevalence of 30-bp LMP1 gene deletion in EBV-positive HD in the United States (US) (12 cases) and Brazil (26 cases) with comparison to reactive lymphoid tissues (21 cases) and HD without EBV-positive Reed-Sternberg cells (15 cases). We studied the status of the LMP1 gene by Southern blot hybridization of polymerase chain reaction (PCR) products obtained after amplification with primers spanning the site of the deletion. We also performed EBV typing, EBER1 in situ hybridization, and LMP1 protein immunohistochemistry. EBV was detected in 12/26 (46%) cases of HD from the US and 26/27 (96%) cases of Brazilian HD. The 30-bp LMP1 gene deletion was observed in 4/12 (33%) cases of EBV-positive HD from US, and 12/26 (46%) cases of Brazilian EBV-positive HD, including 3 cases of type B EBV, as compared with 12/21 (57%) reactive lymphoid tissues and 9/15 (60%) cases of EBV-negative HD. US and Brazilian HD showed a higher prevalence of the 30-bp LMP1 gene deletion, compared with studies of others. The unexpected finding of high incidence of 30-bp deletion in LMP1 gene in reactive lymphoid tissue and HD without EBV-positive Reed-Sternberg cells suggests that this deletion may not be relevant to HD pathogenesis in most cases.

Adolescent↗
PubMed2004

HIV-1 does not provoke alteration of cytokine gene expression in lymphoid tissue after acute infection ex vivo.

The cytokine response to invading microorganisms is critical for priming the adaptive immune response. During acute HIV infection, the response is disrupted, but the mechanism is poorly understood. We examined the cytokine response in human lymphoid tissue, acutely infected ex vivo with HIV. Lymphoid tissue was cultured either as blocks or as human lymphocyte aggregate cultures (HLAC) of tonsils and lymph nodes. This approach allowed us to examine the effects of HIV on cytokines using distinct culture techniques. In contrast to HLAC, mock-infected tissue blocks displayed a 50- to 100-fold up-regulation of mRNAs for IL-1beta, -6, and -8 in the first 6 days of culture. Parallel increases were also noted at the protein level in the supernatants. Although IL-1beta, -6, and -8 are known to synergistically enhance HIV replication, peak HIV replication (measured as p24 Ag) was similar in tissue blocks and HLAC. Surprisingly, vigorous HIV replication of CXCR4- and CCR5-tropic HIV strains did not result in characteristic mRNA profiles for IL-1beta, -2, -4, -6, -8, -10, -12, -15, IFN-gamma, TNF-alpha, TGF-beta, and beta-chemokines in tissue blocks or HLAC. The increased expression of IL-1beta, -6, and -8 in tissue blocks may approximate clinical situations with heightened immune activation; neutralization of these cytokines resulted in inhibition of HIV replication, suggesting that these cytokines may contribute to HIV replication in certain clinical settings. These results also indicate that different molecular mechanisms govern HIV replication in tissue blocks and HLAC. Prevention of effective cytokine responses may be an important mechanism that HIV uses during acute infection.

Adolescent↗
PubMed1995

Cytokine receptor expression in human lymphoid tissue: analysis by fluorescence microscopy.

A highly-sensitive flourescence method, capable of detecting cytokine receptors present at low concentrations (around 100 molecules per cell) by flow cytometry, was adapted for use on tissue sections. This method was used to examine the expression of several cytokine receptors in lymphoid tissues. IL-2 receptors were distributed broadly, with higher concentrations in T cell areas. IL-1 receptor Type 1 was detected in T cell areas and in the follicular mantle, and was strongly expressed on vascular endothelium. IL-6 receptor was found at very low concentration, both within and outside germinal centres. The gp 130 molecule, which is involved in the functional receptor complex for IL-6 and several other cytokines, was present at higher concentrations, particularly in the germinal centre. Analysis of receptor expression in secondary lymphoid tissue provides evidence bearing on the physiological roles of cytokines, as these tissues contain cells at various stages of physiological activation located in well-defined functional zones.

Antibodies, Monoclonal↗
PubMed1998

[Features of the distribution of lymphoid tissue in the walls of the trachea and principal bronchi after exposure to acetaldehyde vapors].

The present study was aimed to examine the lymphoid tissue in the walls of the trachea and major bronchi following the inhalation of acetaldehyde. Albino Wistar rats, subjected to the action of acetaldehyde 20 and 25 mgm/m3 in concentrations during 2, 4, 6, and 8 hrs were the subject of the experiment. It was established that acetaldehyde action in the wall of trachea and major bronchi results in histotopographical changes of lymphoid structures and increase of relative (%) area of lymphoid tissue in the walls of the above-mentioned organs.

Acetaldehyde↗
PubMed1975

Immunological capacity of the chicken embryo. I. Relationship between the maturation of lymphoid tissues and the occurrence of cell-mediated immunity in the developing chicken embryo.

In an investigation of the ontogeny of lymphoid tissue in chick embryos to relate maturation of lymphocytes with immunological competence, the numbers and sizes of lymphocytes were determined in the thymus, bursa of Fabricius, spleen, femoral marrow and peripheral blood of embryos from the 12th to 21st day of incubation, and in 6-day-old chicks. Results showed the thymus to be the first fully developed and most active lymphocytopoietic organ, followed by the bursa. The bone marrow was not lymphocytopoietic; the spleen and bone marrow were mainly granulocytopoietic and erythropoietic; some morphological differences between thymic and bursal lymphocytes were shown by light microscopy. It appears that in embryos and young chicks the lymphocytes are derived from the thymus and bursa, but not the bone marrow. In tests of immunological competency, cells of the thymus, bursa, spleen, bone marrow and peripheral blood from 12--21-day-old embryos and 6-day-old chicks were transferred to chorioallantoic membranes of 12-day-old recipient embryos. There were distinct differences between the ability of various lymphoid tissues to induce formation of chorioallantoic pocks or splenic enlargement. The thymus, spleen and peripheral blood elicited both lymphocytic pocks and splenomegaly, the bursa elicited splenomegaly only, and the bone marrow was ineffective. The bone marrow, however, induced formation of nonlymphocytic pocks. It is concluded that the immunological activity of the chicken embryo is primarily effected by the thymus and bursa and that cell-mediated immunity appears in the 2nd week of incubation.

Age Factors↗
PubMed2002

Expression of the B cell-attracting chemokine CXCL13 in the target organ and autoantibody production in ectopic lymphoid tissue in the chronic inflammatory disease Sjögren's syndrome.

Sjögren's syndrome is an autoimmune disease characterized by lymphocytic infiltrates resembling secondary lymphoid organs in salivary glands. In this study, we demonstrate the expression of the lymphoid tissue homing chemokine CXCL13 (BCA-1/BLC), which has attracting properties for B cells and subsets of activated T cells, in salivary glands of patients with Sjögren's syndrome using immunohistochemistry and in situ hybridization. CXCL13 expression was primarily observed in epithelial cells in acini and ducts of inflamed glands while its receptor, CXCR5 (BLR-1), was expressed on the infiltrating mononuclear cells. In addition, cells producing antibodies against one of the major autoantigens in Sjögren's syndrome, Ro 52, were identified at the periphery of the follicular infiltrates indicating that the ectopic lymphoid tissue is directly involved in the disease process. Identification of CXCL13 and CXCR5 in salivary glands suggests that the target organ plays an essential role in the inflammatory process by recruiting B and T cells. These results also provide a molecular mechanism by which lymphoid neogenesis and ectopic germinal centre formation might occur in the glands of these patients, which may be the key step in the development of the chronic inflammatory process in Sjögren's syndrome.

Autoantibodies↗
PubMed1994

Mucosa-associated lymphoid tissue (MALT) in the human conjunctiva.

The recent description of conjunctival lymphomas with features of lymphomas that arise in mucosa-associated lymphoid tissue (MALT) infers the presence of MALT in the human conjunctiva. Some authors suggest that organized MALT is found in the normal human conjunctiva, but others disagree. In order to resolve this problem, we have examined the conjunctival fornix from unselected autopsies with no prior history of conjunctival or ocular disease for the presence of organized MALT. In only 31 per cent of cases was organized lymphoid tissue found with the morphological and immunophenotypic features of MALT. This finding suggests that MALT is not found in the normal human conjunctiva but is acquired during life in a proportion of apparently asymptomatic individuals.

Adolescent↗
PubMed1997

Topographic distribution of homing receptors on B and T cells in human gut-associated lymphoid tissue: relation of L-selectin and integrin alpha 4 beta 7 to naive and memory phenotypes.

In mice, integrin alpha 4 beta 7 is the main receptor used by lymphocytes that home to the Peyer's patches, although L-selectin contributes to the initial interaction with high endothelial venules. Less is known about the expression and function of these adhesion molecules in humans. The distribution of L-selectin and alpha 4 beta 7 on various B- and T-cell subsets was examined in human Peyer's patches (n = 8) and appendix (n = 4), collectively called gut-associated lymphoid tissue. Multicolor immunophenotyping was performed on cryosections, and dispersed cells were examined by flow cytometry. In cryosections, CD45RA+ T cells around and within interfollicular high endothelial venules, as well as surface (s)IgD+ B lymphocytes in the follicle mantles, often expressed abundant L-selectin but only intermediate levels of alpha 4 beta 7. CD45RO+ T cells and sIgD- B cells expressed higher levels of alpha 4 beta 7 and were often located near putative efferent lymphatics; only a small fraction (< 20%) of such memory cells expressed L-selectin. By flow cytometry, considerably more T than B lymphocytes co-expressed L-selectin and alpha 4 beta 7 (40% versus 25% and 67% versus 39%, respectively). In samples with many L-selectin+ cells (> 30%), more of these lymphocytes co-expressed alpha 4 beta 7 than in samples with few L-selectin+ cells. Because L-selectin and alpha 4 beta 7 were co-expressed on lymphocytes located near high endothelial venules, and because such co-expression was relatively common when many L-selectin+ cells were present, both of these molecules might participate in homing to human gut-associated lymphoid tissue. Such homing is probably most pronounced for T lymphocytes that were found to express L-selectin and alpha 4 beta 7 more often than B lymphocytes. The selective and relatively high expression of alpha 4 beta 7 on memory cells located near efferent lymphatics indicated a different migratory capacity; after exit from gut-associated lymphoid tissue, such stimulated cells might home mainly to mucosal effector sites.

Adolescent↗
PubMed2006

Coincidence of different structures of mucosa-associated lymphoid tissue (MALT) in the respiratory tract of children: no indications for enhanced mucosal immunostimulation in sudden infant death syndrome (SIDS).

Mucosa-associated lymphoid tissue (MALT) is the principal inductive site for mucosal immune responses that are capable of T and B cell responses and antigen-specific responses. In previous independent studies different structures of MALT, e.g. bronchus-, larynx- and nose-associated lymphoid tissue (BALT, LALT, NALT) have been described separately in various frequencies in the human respiratory tract over life spans. Because upper respiratory tract infections are common in infants, dysregulations of mucosal immune responses might be seriously involved in the aetiology of sudden infant death syndrome (SIDS). In the present study the coincidental occurrence of the three different MALT structures in the respiratory tract within the same patients were studied, and cases of SIDS and children who had died from different traumatic and natural causes of death (non-SIDS) were compared. First, the frequency of BALT and LALT in 46 children (35 SIDS, 11 non-SIDS) with or without NALT were examined. A tendency was found of a coincidence of respiratory MALT structures. In 50 additional cases of infant death (30 SIDS, 20 non-SIDS) from the multi-centric German Study on Sudden Infant Death Syndrome (GeSID) where death had occurred in the first year of life, the coincidence was evaluated. A coincidental occurrence of BALT, LALT and NALT or BALT and LALT (each about 30%) was found in both groups, whereby the coincidence in SIDS and the control patients did not differ. Interestingly, the children with coincidental MALT were strikingly older, supporting the hypothesis of respiratory MALT formation via environmental stimulation over time.

Bronchi↗
PubMed1998

Confocal microscopy assessment of lymphoid tissues with follicular hyperplasia from patients infected with human immunodeficiency virus type 1.

OBJECTIVE: To characterize human immunodeficiency virus (HIV) infection of lymphoid tissues during follicular hyperplasia. METHODS: We examined 10 tonsil/adenoid, 3 parotid lymphoepithelial cyst, and 7 lymph node specimens that had been surgically removed from 13 patients infected with HIV-1. Characteristics of productive HIV-1 infection were assessed using immunocytochemistry for HIV-1 p24. Cellular colocalization was determined with the aid of a confocal microscope using double immunofluorescent staining for HIV-1 p24 and cell-specific markers. RESULTS: All specimens showed follicular hyperplasia. Using confocal microscopy with three-dimensional reconstruction, HIV-1 p24 was seen to be "intimately" colocalized with CD21 within the germinal centers. While lymphoid follicles were generally hyperplastic, only a subset of these follicles contained HIV-1 p24. Occasional HIV-1-expressing mononuclear cells identified outside follicles stained for CD68 or CD3. CONCLUSIONS: The differential involvement of hyperplastic follicles by HIV-1 within individual lymphoid tissues and the intimate colocalization of HIV-1 p24 and CD21 suggest that infected follicular dendritic cells may be an important reservoir of HIV-1 during follicular hyperplasia.

Adult↗
PubMed2002

Lack of Shiga-like toxin binding sites in germinal centres of mouse lymphoid tissues.

B cells in germinal centres are known to express carbohydrate antigen CD77 in human lymphoid tissues. The CD77 antigen is specifically recognized by Shiga-like toxins (SLTs) that are produced by enterohaemorrhagic Escherichia coli O157:H7. To determine whether the binding subunits of Shiga-like toxin-1 (SLT-1B) could have adverse effects on the murine immune system when used as an immunogen, we investigated whether SLT-1B could bind to germinal centres of mouse lymphoid tissues. Frozen sections of peripheral lymph nodes and Peyer's patches from immunized mice were tested for the presence of SLT-1B-binding sites by immunohistological methods. Germinal centres were not stained with SLT-1B, while they were intensely stained with peanut agglutinin (PNA), another marker of germinal centres. On the other hand, SLT-1B specifically bound to renal tubules and collecting ducts in frozen sections of mouse kidney. This is consistent with results from human tissues. We also demonstrated that B220/PNA double-positive populations in lymph nodes from immunized mice exhibited only marginal staining with SLT-1B. The present results suggest that SLTs would not impede germinal centre functions of the murine immune system.

Animals↗
PubMed1983

Relation between mucous cells and lymphoid tissue in rat intrapulmonary airways.

The distribution of mucous cells in rat intrapulmonary airways was investigated by conventional light microscopic technique. A striking association was found between differentiation of epithelial mucous cells and accumulation of lymphoid tissue in the lamina propria of bronchioli. Nodular accumulations of lymphoid tissue, covered by a lymphoepithelium, as well as differentiation of mucous cells, increased with age. This normal development was accelerated in rats exposed to aerosolized ovalbumin.

Aging↗