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R Pabst

Publications and source records attributed to R Pabst.

At least 127 records · Page 7Linked to original sources
PubMed1995

The neuropeptide substance P does not influence the migration of B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes from blood to lymph in the normal rat.

Thoracic duct lymphocytes (TDL) continuously patrol through the body, facilitating immune responses at most sites. The neuropeptide Substance P might regulate immune responses by influencing the migration of TDL. Therefore, it was investigated whether Substance P affects the migration of thoracic duct B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes from blood to lymph in vivo. Labelled TDL were either incubated with Substance P and then injected into normal rats, or incubated without Substance P and then injected into rats continuously receiving Substance P intravenously. The numbers of labeled B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes were determined in blood and thoracic duct lymph for 1 and 5 days, respectively. Neither the in vitro incubation with Substance P nor its in vivo application influenced the disappearance of any lymphocyte subset from the blood or its reappearance in the lymph. In addition, continuous intravenous application of the Substance P antagonist CP 96.345 did not alter the volume or the lymphocyte number of the efferent lymph. The present study indicates that the nervous system does not influence immune responses via Substance P by altering the migration pattern of B, T, CD8+ and CD4+ ('naive' and 'memory') lymphocytes.

Animals↗
PubMed1995

Bronchus-associated lymphoid tissue (BALT) in the lungs of children who had died from sudden infant death syndrome and other causes.

BACKGROUND: Bronchus-associated lymphoid tissue (BALT) is well characterised in rabbits and rats. In humans, however, it does not seem to be present in the healthy adult lung, although it can develop after certain microbial stimulation. METHODS: In the present study a consecutive series of lungs from 88 children who had died of sudden infant death syndrome (SIDS) and 34 control cases of comparable age were examined for the presence of BALT. RESULTS: BALT was present in 36.4% of the patients who had died of SIDS and in 44.1% of the control cases. The probability of finding BALT increased with age, with similar kinetics in both groups. CONCLUSIONS: Future studies need to define when and at what rate BALT disappears as children get older. In young children BALT may act as an entry site for antigens to initiate an immune response, as is well documented for the gut-associated lymphoid system.

Age Factors↗
PubMed1995

Lymphocytes migrate from the bronchoalveolar space to regional bronchial lymph nodes.

The fate of lymphocytes in the bronchoalveolar tract was studied in normal young pigs. Peripheral blood lymphocytes were labeled with 51chromium or with fluorescein isothiocyanate (FITC) and instilled into a single segmental bronchus. In the first series of experiments, the radioactivity was determined in several different parts of the lungs, individual bronchial lymph nodes and a series of other lymphoid and nonlymphoid organs. About two-thirds of the radioactivity was still in the lung at 1 d. The draining lymph node also contained high amounts of radioactivity. To exclude that this was caused by labeled cell debris, an immunohistologic technique was used to localize the FITC-labeled cells. There were clearly labeled lymphocytes in the sinusoids of the draining nodes. These lymphocytes were characterized by additional surface staining. B, T, TH, and TS lymphocytes were seen much less often than in the inoculum while the null and gamma delta T cells showed a preference. The lymphocytes reached the bronchial lymph nodes via lymphatics. Lymphocytes in the bronchoalveolar space are not effete cells to be destroyed but return to the immune system. These data provide new interest in the immunologic role of lymphocytes in the bronchoalveolar tract and their kinetics.

Animals↗
PubMed1995

The rabbit M-cell marker vimentin is present in epithelial cells of the tonsil crypt.

The epithelium of the rabbit palatine tonsil was studied with vimentin immunohistochemistry, using cryosections and paraffin sections labelled with three monoclonal antibodies. Vimentin-positive epithelia[ cells were detected in crypt regions overlying lymphoid follicles but were absent from the surrounding stratified pharyngeal epithelium. The cells lay in close contact with intra-epithelial lymphocytes and their apical cytoplasm had a membranous shape. Since vimentin is a sensitive, specific marker for M-cells of the rabbit intestine, the present findings indicate that M-cells similar to those in the gut-associated lymphoid tissue occur in the tonsil.

Animals↗
PubMed1994

Migration of so-called naive and memory T lymphocytes from blood to lymph in the rat. The influence of IFN-gamma on the circulation pattern.

It has been suggested that naive T lymphocytes migrate directly from the blood into the lymph nodes, whereas memory T lymphocytes arrive via the afferent lymphatics. However, these routes were defined indirectly by determining only the frequencies of naive and memory T lymphocytes in the afferent and efferent lymph of sheep. In this study naive (CD45RC+) and memory (CD45RC-) CD4+ lymphocytes obtained by thoracic duct cannulation of the rat were injected i.v. and their reappearance in the thoracic duct lymph (efferent lymph) was monitored in absolute numbers over 5 days. In addition, it was investigated whether continuous application of IFN-gamma influences the migration of the two subsets differently. After i.v. injection both naive and memory T lymphocytes returned to the thoracic duct in considerable numbers and with similar kinetic patterns. Interestingly, within 5 days at least 25% of memory phenotype lymphocytes converted to naive phenotype lymphocytes. When naive and memory T lymphocytes were injected in animals receiving a continuous IFN-gamma infusion, only the reappearance of the naive T lymphocytes but not that of memory T lymphocytes in the thoracic duct lymph was reduced. Thus, by investigating the migration of labeled lymphocytes, data were obtained that contradict conclusions drawn by analyzing preferential accumulation of lymphocyte subsets only. Our results suggest that in unstimulated animals naive and memory thoracic duct lymphocytes migrate at a similar tempo and to a comparable extent from the blood via the lymph node into the efferent lymph. IFN-gamma only influences the traffic of naive lymphocytes, indicating that the migration of the two populations is regulated by different mechanisms.

Animals↗
PubMed1994

Development of the high endothelial venule in rat lymph node autografts.

Vascular reconstruction during rat lymph node regeneration was investigated in autotransplanted mesenteric lymph node fragments, which had been implanted in the renal parenchyma. In addition to light microscopy, vascular casting and transmission electron microscopy were used. From day 3 onwards capillaries grew into the autografts together with lymphatic vessels. The capillaries showed obvious signs of proliferation by day 5. The surviving interstitial cells at the outer border of the transplant produced extracellular substance. High endothelial venules (HEV) differentiated from capillaries from about day 7. A first sign of their development was a vessel with a narrow, branching luminal space and with endothelial cells containing rich cytoplasm and small Golgi complexes. As the Golgi complexes grew and the cisternae and vesicles increased, the lumen dilated, the cell coat on the luminal surface became prominent, and, finally, lymphocytes emigrated through these venules from around day 10. The typical lymph node structure was complete by day 28. These results suggest that the interaction among the remaining interstitial cells, invading capillaries, and lymphatic penetration results in differentiation and maturation of HEV in lymph node regeneration. The development of Golgi complexes is strongly associated with lymphocyte emigration from the blood.

Animals↗
PubMed1994

B and T lymphocyte subsets enter peripheral lymph nodes and Peyer's patches without preference in vivo: no correlation occurs between their localization in different types of high endothelial venules and the expression of CD44, VLA-4, LFA-1, ICAM-1, CD2 or L-selectin.

Many lymphocytes enter tissues such as peripheral lymph nodes, and Peyer's patches through high endothelial venules (HEV). It is known that HEV differ in the expression of adhesion molecules as lymphocyte subsets do. Through the interaction of these molecules B and T lymphocyte subsets are thought to be preferentially directed into lymphoid organs. However, it is unclear which role these mechanisms play in vivo, since there are no studies demonstrating that blood lymphocyte subsets preferentially interact with different types of HEV in vivo. Therefore, in the present study the frequency of B, T, CD4+ and CD8+ lymphocytes in the wall of the HEV of rat peripheral lymph nodes and Peyer's patches was analyzed by immunohistology. In addition, the expression of CD44, VLA-4, LFA-1, ICAM-1, CD2 and L-selectin on B and T lymphocyte subsets of the blood was determined by flow cytometry. Although B and T lymphocytes showed significantly different levels of expression for each adhesion molecule investigated, the relation of B and T lymphocytes within the HEV of peripheral lymph nodes and Peyer's patches was strikingly comparable (38.0 +/- 5.2% vs. 40.6 +/- 5.7% and 62.0 +/- 5.2% vs. 59.4 +/- 5.7%, respectively). The same was true for CD4+ and CD8+ cells. Thus, although HEV and the blood lymphocyte subsets differ markedly in their expression pattern of adhesion molecules, the existing levels are sufficient to mediate comparable entrance of B and T lymphocyte subsets into both types of HEV.

Animals↗
PubMed1994

Many newly formed T lymphocytes leave the small intestinal mucosa via lymphatics.

The results show that 50% of the IgA+ and 25% of the IgM+ cells that leave the gut are newly formed BrdU+ cells. However, in absolute numbers the BrdU+Ig+ lymphocytes are the smaller cell pool in the afferent lymph, 2 to 3 times more newly formed T cells were observed. The function of this unexpectedly large pool of newly formed T lymphocytes in oral immunity or tolerance has to be clarified. In a recent study Dunkley and Husband reported that non-B cells play an important role for the localization of plasma cell precursors in the lamina propria of the mucosa. So far it is unknown where the pool of newly formed T and Ig+ lymphocytes comes from. Partially they are produced in the PP. However, they may have their origin in the lamina propria of the mucosa as well as in other organs of the body. Further studies are necessary to characterize the origin and the function of the large numbers of newly produced T lymphocytes in the intestinal lymph.

Animals↗
PubMed1994

Cytokeratin 18 is an M-cell marker in porcine Peyer's patches.

The intermediate filaments of the dome epithelium of porcine Peyer's patches were studied by immunohistochemistry. The labelling patterns of monospecific antibodies directed against cytokeratins 8, 18 and 19 differed considerably. About 40% of the dome epithelial cells were intensely labelled by three different anti-cytokeratin 18 antibodies, indicating that large amounts of cytokeratin 18 are present in these cells. In order to verify that these cytokeratin-18-immunoreactive cells were M-cells, uptake studies using fluorescein-labelled yeast particles were performed. Numerous yeast particles were found exclusively in dome epithelial cells that were highly positive for cytokeratin 18, thus representing M-cells. In contrast, the content of cytokeratin 19 in M-cells was lower than that in neighbouring enterocytes. The labelling intensity of cytokeratin 8 did not differ between M-cells and enterocytes. In addition, the absence of vimentin and desmin from the dome epithelium of porcine Peyer's patches was demonstrated. The results show (1) that porcine M-cells differ from enterocytes in the composition of their cytoskeleton, (2) that cytokeratin 18 is a useful marker for detecting porcine M-cells and (3) that this marker directly correlates with M-cell function.

Animals↗
PubMed1994

The unique ultrastructure of high-endothelial venules in inguinal lymph nodes of the pig.

Lymph nodes in pigs are unique in their inverted structure, with the medulla in the periphery and the cortex in central areas. Furthermore, in this species most migrating lymphocytes do not use the classical route via efferent lymphatics to leave the lymph node. High-endothelial venules (HEV) are the entry sites for lymphocytes and in pigs probably also the exit site for recirculating lymphocytes. Therefore, the blood vessels and especially the HEV of the pig superficial inguinal lymph node were investigated as to whether morphological peculiarities could be found in the vascular system, using vascular casting, transmission- and scanning electron microscopy. A thin layer of capillary network surrounded the periphery of the lymph node and HEV branched acutely. The endothelial cells of HEV possessed well developed cytoplasmic organelles, interdigitated with each other, and demonstrated local cell-cell contacts. There were unusual cells bridging the adluminal wall of HEV. These cells were called intravascular bridging cells. They were characterized by an often invaginated nucleus, few pinocytotic vesicles, many microvilli on the surface, wide, flat, cytoplasmic processes like a pseudopod, Weibel-Palade bodies and local cell-cell contacts with endothelial cells. The pseudopod-like processes ramified over the endothelial junctions and covered lymphocytes. Lymphocytes were seen in different phases of migration between endothelial cells and in the intercellular junctions. The previous functional studies on the peculiar route of lymphocyte recirculation in pig lymph nodes are extended by these morphological data, showing a unique structure of HEV in pigs.

Animals↗
PubMed1994

Lymphoid tissue structure and lymphocyte trafficking in the pig.

The organised lymphoid tissues of the pig, though conventionally mammalian in most respects, show several distinctive properties in their structure and physiology. Specialised antigen-presenting lymphoid organs function at three compartmental levels: the body surfaces, their draining lymph nodes and the spleen in the bloodstream. Other organs act as lymphocytic depots and sites of phagocytosis of debris. Pig lymphocytes recirculate continuously through these organs and through different forms of inflammatory change, experimentally induced by mitogens and cytokines, using a spectrum of distinctively different physiological mechanisms. These tissues in the young pig differ both in the resting and activated cell subsets and the molecules involved, many of which remain to be completely defined. Intriguing insights are evident in the subtlety of regulation of the specificity, level and foetal ontogeny of trafficking mechanisms in these different tissues, though they are as yet poorly explained. This subtle molecular physiology is only now emerging because appropriate monoclonal antibody reagents are being developed and rigorous attention is being paid to the use of gentle physiological methods in experiments in vivo.

Animals↗
PubMed1994

The immune system of the respiratory tract in pigs.

Although the lung is not a lymphoid organ it contains large numbers of lymphocytes. These can be found in different compartments: (1) the pulmonary intravascular pool, which is organ-specific and shows a unique migration pattern; (2) the interstitial lymphocyte pool, which is equivalent in size to the whole blood pool; (3) the bronchus-associated lymphoid tissue (BALT) which develops as a result of microbial stimulation; (4) the intraepithelial and lamina propria lymphocytes of the bronchi, with their typical subset composition; (5) the lymphocytes in the bronchoalveolar space, which can be sampled by bronchoalveolar lavage. The size and kinetics of the lymphocyte pools have been studied in the pig in more detail than in most other species. Despite this organotypic compartmentalisation of the pulmonary lymphoid cells in the pig, the lung is part of the integrated mucosal immune system, as shown by protective oral immunisation against the lung-pathogenic bacteria Actinobacillus pleuropneumoniae. The lung immune system in the pig is not only of veterinary interest, but also a relevant model for the human respiratory tract.

Actinobacillus Infections↗
PubMed1994

Which steps in lymphocyte recirculation are regulated by interferon-gamma?

Lymphocyte traffic throughout the body is a basic mechanism of immune surveillance. Most studies of the regulation of the extravasation of lymphocytes have focused on the interaction between endothelial cells of the high endothelial venules (HEV) in lymphoid organs and lymphocytes via the interaction of various adhesion molecules. Cytokines play a major role in the regulation of immune reactions, and some have been shown to upregulate adhesion molecules important for lymphocyte migration. Using interferon-gamma (IFN gamma) as an example of such a cytokine, we summarize the available data on regulation by IFN gamma of the different phases of lymphocyte migration from the blood via HEV, through the lymphoid organ and finally exiting the organ. Much data obtained in in vitro assays have not yet been confirmed in vivo, and therefore a number of questions remain unanswered. Our hypothesis is that the interaction of lymphocytes with endothelial cells represents just one aspect of regulation, and that lymphocyte migration is probably regulated much more effectively within the lymphoid organ.

Animals↗
PubMed1994

Oral and aerosol immunization with viable or inactivated Actinobacillus pleuropneumoniae bacteria: antibody response to capsular polysaccharides in bronchoalveolar lavage fluids (BALF) and sera of pigs.

To investigate the antibody response after local application of lung-pathogenic bacteria, pigs were immunized with viable or inactivated Actinobacillus pleuropneumoniae by the oral and aerogenous route. After 3 weeks class-specific immunoglobulins against purified A. pleuropneumoniae capsular polysaccharides (CP) were determined in serum and BALF by ELISA. A significant increase of IgA antibodies was found in BALF but not in sera of all immunized pigs. Oral immunization with viable A. pleuropneumoniae and aerosol immunization with either viable or inactivated bacteria resulted in a significant increase of IgG antibodies to the CP antigen in BALF, whereas only aerosol exposure to viable bacteria resulted in a significant increase in IgG antibodies in serum. A significant increase in anti-CP IgM in BALF was observed after aerosol exposure but not after oral immunization. IgM antibodies towards CP increased significantly by both routes of immunization with viable bacteria. The anti-CP activity of all three isotypes in sera and BALF was low in all groups compared with the positive controls, although inoculation of viable A. pleuropneumoniae led to higher levels of antibody concentration than inactivated bacteria. Our results indicate a traffic of primed lymphocytes from the gut into the bronchoalveolar airways and further support the hypothesis that polysaccharide-specific B cells may functionally mature at the mucosal surfaces.

Actinobacillus pleuropneumoniae↗
PubMed1994

B- and T-lymphocyte subset numbers in the migrating lymphocyte pool of the rat: the influence of interferon-gamma on its mobilization monitored through blood and lymph.

The subset composition of the migrating lymphocyte pool is largely unknown. In order to determine the number of B, T, CD8+, CD4+ and CD4+ 'naive' (CD45RC+) and 'memory' (CD45RC-) lymphocytes in this pool, the thoracic duct lymph of the rat was drained for 7 days. The effect of lymphocyte depletion on the number of blood lymphocytes was also monitored. In addition, the influence of continuously applied interferon-gamma (IFN-gamma) on the mobilization of the migrating lymphocyte pool was investigated. Within 1 week 2 x 10(9) thoracic duct lymphocytes (TDL) were collected, which represents about 50% of the total lymphocyte pool of an adult rat. Among the migrating lymphocytes an early and a late mobilized population could be differentiated. In the former the CD4+ 'naive' (CD45RC+) T lymphocytes constituted the largest population, whereas in the latter it was the B lymphocytes. Continuous infusion of IFN-gamma did not affect the number of lymphocytes in the blood. In contrast, in the thoracic duct IFN-gamma reduced the appearance of all lymphocyte subsets. However, the pattern of reduction over time differed markedly depending on the population (early or late mobilized) and the phenotype (B- or T-lymphocyte subsets). Thus, the migrating lymphocyte pool of the rat is very heterogeneous regarding its populations and shows complex changes in the mobilization pattern after IFN-gamma stimulation. Future studies should focus on how the size and the composition of the migrating lymphocyte pool is regulated.

Animals↗