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Biomedical subjects

G Mayrhofer

Publications and source records attributed to G Mayrhofer.

At least 73 records · Page 4Linked to original sources
PubMed1986

Functional characteristics of the veiled cells in afferent lymph from the rat intestine.

Non-lymphoid veiled cells (VC) in the thoracic duct lymph from mesenteric lymphadenectomized rats have been studied by light microscopy, enzyme histochemistry and scanning electron microscopy. These cells arise in the afferent lymph from the intestine. They have been semi-purified and examined for expression of Ia antigens using an indirect immunoperoxidase technique and monoclonal antibodies. Accessory cell function necessary for mitogen-induced blastogenesis in the thoracic duct lymph from these animals has been correlated with the presence of VC by depletion and reconstitution experiments. Similar results were obtained with lymphocyte suspensions from other rat lymphoid organs and they are contrasted with those from studies on mouse lymphoid cells. Antigen presentation in a secondary in vitro lymphoproliferative assay was also depleted from immunized lymph node cells by removal of endogenous VC and can be reconstituted in a dose-dependent fashion with antigen-pulsed VC from afferent intestinal lymph. In contrast, reconstitution of both mitogen-induced blastogenesis and antigen-induced lymphoproliferation with peritoneal exudate cells was poor, while at high multiplicities of added macrophages, such cells were inhibitory. Afferent intestinal lymph VC were found to transport bacteria and bacterial antigen in rats infected with Salmonella typhimurium. The results are discussed in relation to the lineage of the VC in intestinal afferent lymph, their function as accessory cells and their possible physiological role in transporting antigens from the gut to its regional lymph nodes.

Animals↗
PubMed1985

The role of the thymus in the maintenance of natural killer cells in vivo.

This report describes a model for investigating the role of the thymus in regulating natural killer (NK) cell activity in vivo. Evidence is presented that the thymus can regulate NK cells, and that at least some NK cells can develop without thymic help. Marrow from thymectomized rats depleted of circulating T cells by thoracic duct cannulation was transplanted into rats without a thymus (1 degree ATX.BM). These 1 degree ATX.BM rats had NK cell levels above controls 3 months after reconstitution but markedly depressed NK cell levels by 9 months. When 1 degree ATX.BM marrow was used to reconstitute rats with or without a thymus, those without a thymus (2 degrees ATX.BM) exhibited low NK cell levels after 3 months, and a similar result was obtained when 2 degrees ATX.BM marrow was used to reconstitute 3 degrees ATX.BM rats. The low NK cell levels in 2 degrees and 3 degrees ATX.BM rats were due to a deficiency in spontaneously cytotoxic NK cells, as they had normal numbers of interferon-responsive pre-NK cells. Spleen cells from 2 degrees and 3 degrees ATX.BM rats produced less interferon than control spleen cells when cultured with P815 tumor cells in vitro. However, 2 degrees and 3 degrees ATX.BM rats had higher numbers of large granular lymphocytes than controls despite their low NK cell levels. In marked contrast to 2 degrees and 3 degrees ATX.BM rats, spleen cells from 4 degrees ATX.BM rats had higher levels of cytotoxicity and a higher frequency of both spontaneously cytotoxic and pre-NK cells than controls. The 4 degrees ATX.BM rats also had the highest frequency of large granular lymphocytes in the spleen.

Animals↗
PubMed1984

Origins of serum IgE and of the homocytotropic antibody-secreting cells in the thoracic duct lymph of rats infested with Nippostrongylus brasiliensis.

Mesenteric lymphadenectomy caused a marked reduction in the amounts of both parasite-specific and total IgE in the serum of Nippostrongylus brasiliensis infested rats. This was accompanied by reduced quantities of IgE in the thoracic duct lymph, showing that the mesenteric lymph node is of great importance in the generation of the elevated IgE levels which accompany this infestation. Conversely, the intestinal lamina propria and the Peyer's patches did not appear to be significant contributors to either thoracic duct lymph or serum IgE levels. Homocytotropic antibody-secreting cells specific for parasite antigens were detected in the thoracic duct lymph of lymphadenectomized rats and are believed to arise directly from the gut mucosa and possibly from Peyer's patches.

Animals↗
PubMed1984

Kinetics of intestinal lamina propria mast cells, globule leucocytes, intraepithelial lymphocytes, goblet cells and eosinophils in murine strongyloidiasis.

The changes in numbers of 6 cell populations in the intestine of mice at various intervals after primary and challenge infections with Strongyloides ratti have been quantified. The number of lamina propria mast cells increased 8 days after primary infection and reached a peak at 12 days. After secondary infection, there was a transient fall in mast cell numbers followed by a slow increase. Globule leucocytes showed a similar trend early in the primary infection and had reached normal levels after 28 days. After challenge infection, there was an early and rapid increase in their numbers. Granular intraepithelial lymphocytes did not alter significantly during the first 14 days, but were significantly greater 28 days after primary infection; they did not vary significantly after challenge infection. However, numbers of non-granular intraepithelial lymphocytes increased 10 days after infection, were elevated prior to the secondary infection at 28 days, then declined in numbers nearly 2 weeks after challenge infection. Goblet cells increased significantly 12 days after primary infection then declined rapidly. After challenge infection, there was an accelerated increase in numbers. Eosinophil numbers increased 4 days after infection, reached a peak at 12 days and then declined. After challenge infection, there was an augmented and accelerated increase in eosinophil numbers followed by rapid decline. The role of the various cells types in host defences against worms or in containment of the inflammatory responses evoked by these parasites are discussed.

Animals↗
PubMed1983

Ia antigens in rat kidney, with special reference to their expression in tubular epithelium.

The distribution of Ia antigens in rat kidneys has been investigated by an immunoperoxidase technique, using monoclonal antibodies directed at framework determinants on molecules equivalent to gene products of the I-A and I-E/C regions of the mouse major histocompatibility complex (MHC). Antigens mapping to both loci were detected in proximal convoluted tubule epithelium and on scattered dendritic cells in the interstitial connective tissues, glomeruli, and mucosa of the renal pelvis. All other structures were negative. Genetic studies indicate that the levels of expression of Ia molecules from both genetic loci are controlled by non-MHC genes in epithelium, but not on lymphocytes. The subcellular distribution of Ia molecules has been investigated in tubular epithelium and is discussed in relation to their possible functions in epithelia.

Animals↗
PubMed1983

The distribution, ontogeny and origin in the rat of Ia-positive cells with dendritic morphology and of Ia antigen in epithelia, with special reference to the intestine.

Ia antigens were localized in cryostat sections of rat intestine and other tissues by an indirect immunoperoxidase technique using monoclonal antibodies that recognize the rat antigens homologous to the gene products of the I-A and I-E subregions of the mouse major histocompatibility complex (MHC). Two categories of Ia+ cells were characterized, namely epithelial cells and bone marrow-derived cells with dendritic morphology. In the small intestine Ia antigen was present in the distal 2/3 of the absorptive epithelium but absent from the bases of the villi, the crypts and the epithelium covering the Peyer's patches. The distribution in nude rats was similar, indicating that T lymphocytes are not obligatory for its expression. In ontogeny Ia antigen was absent in the epithelium of neonatal gut, appearing at about 4 weeks of age and reaching adult levels at about 6 weeks. Different rat strains showed large differences in the amount of Ia antigen expressed by villus epithelium and the traits for the level of expression were shown to map outside the MHC. The levels of expression of Ia antigen in the proximal tubules of the kidney followed that of the gut epithelium in the different strains and in both tissues was mostly intracellular. Studies with chimeras showed that the Ia antigen in epithelial cells was not acquired from bone marrow-derived cells. The second category of cell studied had a characteristic dendritic morphology and was present in large numbers in the lamina propria of the villi and in the crypts. In the Peyer's patches these cells were present both in the subepithelial dome region and within the epithelium itself. These Ia+ dendritic cells were present in nude rat jejunum and appeared in normal fetal gut by 18 days gestation and were also shown to migrate into antigen-free grafts of fetal gut. This suggests that they do not require stimulation from antigens, bacterial products or T lymphocytes in order to localize in the gut or to express Ia antigen. Studies with other cell surface markers suggest that the Ia+ cells with dendritic morphology represent a range of cell types, some with similarities to macrophages and others to nonphagocytic dendritic cells.

Age Factors↗
PubMed1983

Local and systemic factors regulating mucosal mast cells.

The contributions of local and systemic factors to the regulation of mucosal mast cells and globule leukocytes have been examined in the rat. Nippostrongylus brasiliensis has been used to provide a potent immunological stimulus for mucosal mast cell hyperplasia and the roles of intestinal and extraintestinal sensitization observed by comparison of the gut mast cell responses to larval and adult worm infestations. Systemic effects of adult worm infestations have been examined in isolated Thiry-Vella loops of intestine. It is concluded that the extraintestinal phase of larval infestation is not obligatory for a gut mast cell response and that mast cell hyperplasia and globule leukocyte formation are not dependent on direct contact with the parasite or its products. The dissemination of the mast cell response and the general significance of the results are discussed.

Animals↗
PubMed1983

Granular intraepithelial lymphocytes of the rat small intestine. I. Isolation, presence in T lymphocyte-deficient rats and bone marrow origin.

Intraepithelial lymphocytes have been studied in the small intestinal epithelium of normal and thymus-deficient rats. A method is described that allows recovery of purified intraepithelial lymphocytes with high yield and viability. Granular intraepithelial lymphocytes were present in normal numbers in jejunal sections from nude rats and from adult thymectomized, irradiated, bone marrow-reconstituted rats. These probably corresponded to the cells with prominent cytoplasmic granules seen in smears of isolated intraepithelial lymphocytes. Studies in athymic chimeras indicated that both granular and nongranular intraepithelial cells differentiate from bone marrow without requirement for thymus processing and that they are relatively more radio-resistant than classical lymphocytes. It is suggested that all or most intraepithelial lymphocytes form a single cell lineage in which the degree of cytoplasmic differentiation is controlled by either the thymus or T lymphocytes. Intraepithelial lymphocytes are not postthymic T cells and their relationship to mucosal mast cells and to natural killer cells is discussed.

Animals↗
PubMed1983

Natural cytotoxicity, responsiveness to interferon and morphology of intra-epithelial lymphocytes from the small intestine of the rat.

The expression of natural cytotoxicity in the gut-associated lymphoid tissue of the rat was investigated. Intra-epithelial lymphocytes (IEL) isolated from the small intestine had a similar frequency of cytotoxic and tumour target binding cells as the spleen. However, cytotoxic activity was low in Peyer's patches and mesenteric lymph node. Cytotoxic IEL exhibited similar target-cell specificity to splenic natural killer (NK) cells, and substantial antibody-dependent cell-mediated cytotoxicity. However, their cytotoxicity and lytic efficiency was not rapidly increased following exposure to interferon and IEL probably contain only a relatively small pool of pre-NK cells. IEL contained approximately 50% of cells with basophilic cytoplasmic granules, compared to approximately 2% of granule-containing mononuclear cells in the spleen. Direct observation using the uptake of acridine orange to detect cytoplasmic granules established that some cytotoxic IEL were granular. However, substantial cytotoxicity was also mediated by non-granular IEL and not all granular IEL which bound to target cells were cytotoxic. Counts of granulated cells in Giemsa-stained preparations of spleen cells and results from single-cell assays using unfractionated splenocytes suggest that the majority of target-binding cells and at least half of the naturally cytotoxic cells must also be non-granular.

Animals↗
PubMed1981

Bone marrow origin of Ia-positive cells in the medulla rat thymus.

Irradiated rats were reconstituted with bone marrow from F1 hybrids. Ia antigen of donor-bone marrow origin was detected by an immunoperoxidase technique on cryostat sections and found predominantly in the medulla of rat thymus 2 wk after reconstitution. These Ia-bearing cells increased in number with time after reconstitution, but the Ia on the cortical epithelial cells remained of host origin. The nature of the bone marrow-derived cells and their implication for major histocompatibility complex restriction are discussed.

Animals↗
PubMed1981

Age-dependent modulation of serum IgE and mast cell sensitization by Nippostrongylus brasiliensis infestation in rats.

The capacity of N. brasiliensis (Nb) infestation to modify synthesis of ovalbumin (OV) specific IgE antibody was monitored in weanling, juvenile and adult female WAG rats by both passive cutaneous anaphylaxis (PCA) activity and by a rat radio-allergosorbent test (RAST). Infestation with Nb larvae 10 days after immunization with OV produced marginal potentiation of anti-OV Ig antibody production by both RAST and PCA in weanlings, marginal suppression by both parameters in juveniles and was without effect in adults. However, immunization with OV after infestation with Nb partially suppressed anti-OV IgE antibody production in weanlings (RAST) and totally abolished the PCA activity. Although this regime did not impair anti-OV IgE antibody synthesis (RAST) in juveniles, the sera were PCA-negative. In contrast, normal responses were found in adult rats. Negative PCA titres in sera containing high levels of specific antibody occurred when serum total IgE levels were elevated, and are explained on the basis of competition for binding sites on mast cells. The ratio of OV-specific IgE to 'total' IgE is a critical factor in detecting PCA activity.

Animals↗
PubMed1981

The distribution and traffic of specific homocytotropic antibody-synthesizing cells in Nippostrongylus brasiliensis-infested rats. Comparison of synthesis with the kinetics of antibody and IgE levels in serum and lymph.

Synthesis of specific homocytotropic antibody by cells from various lymphoid and haemopoietic organs in rats infested with Nippostrongylus brasiliensis has been studied by use of homologous adoptive cutaneous anaphylaxis and compared with the kinetics of appearance in the serum and thoracic duct lymph of specific IgE antibodies. Using this technique, synthesis of specific mast cell-sensitizing antibody has been detected in the draining lymph nodes of the lung as early as 12 days after infestation and by 14 days in the draining lymph nodes of the small intestine. Specific IgE antibody was not detected in serum until between 16 and 18 days after infestation. The delay in detection of antibody in the serum is at least in part due to its rapid removal from the blood, because antibody en route to the bloodstream from the gut-associated lymphoid tissue was detected in the thoracic duct lymph plasma as early as day 12. A major traffic of homocytotropic antibody-secreting cells has been detected in the thoracic duct lymph of the infested rats. The results are discussed in terms of the possible role of immediate hypersensitivity in the expulsion of the parasite, the origin of the IgE antibody response to the parasite and the mechanism of the potentiated reagin response.

Animals↗
PubMed1981

Nature of the thymus dependency of mucosal mast cells. III. Mucosal mast cells in nude mice and nude rats, in B rats and in a child with the Di George syndrome.

Mucosal mast cells have been examined in the small intestinal mucosae of nude mice and nude rats, B rats and a child with the DiGeorge syndrome. In all three species, mast cells were present in normal numbers despite the athymic status of the nude mice and nude rats, the vestigial nature of the thymus in the child, and the functionally T lymphocyte-deprived status of the B rats. Connective tissue mast cells were also plentiful in skins and tongues of the nude mice and the child with thymic aplasia. It is concluded that normally neither population of mast cells has a obligatory dependence on the thymus or T lymphocytes for its differentiation, but that mucosal mast cells, under certain conditions of rapid hyperplasia, require an inductive influence provided by T lymphocytes.

Animals↗
PubMed1981

Alveolar macrophages. VI. Regulation of alveolar macrophage-mediated suppression of lymphocyte proliferation by a putative T cell.

Alveolar macrophages (AM) from normal rats suppressed antigen- or mitogen-stimulated blastogenic responses in cultures of splenic or lymph node lymphocytes, high levels of suppression often being observed when added AM comprised as few 0.6% of the total cells in culture. The efficiency of AM-mediated suppression of spleen cell blastogenesis declined with the age of the spleen cell donors, was severely curtailed by pretreatment of donors with low levels of cyclophosphamide, and was depleted by adult thymectomy coupled with thoracic duct drainage. The suppressive activity of AM was most obvious at high cell density, was unaffected by the presence of indomethacin in the cultures, or by prior X-irradiation of the spleen cells. Fractionation of spleen cells by velocity sedimentation yielded cell populations of greatly varying sensitivities to AM-mediated suppression, from small splenocytes (sedimentation velocity 1.1-2.8 mm/h) which were almost totally refractory to AM-suppression when assayed in isolation from the remainder of the spleen cell population, to larger cells (sedimentation velocity greater than 3.,5 mm/h) exhibiting high levels of sensitivity. Fractionation of spleen cells by glass wool adherence indicated decreased sensitivity to AM-suppression in the effluent population. Examination of the suppressive activity of individual subpopulations of AM separated by velocity sedimentation indicated that the larger macrophages were the most active in vitro. Suppressive activity of this nature was not seen with unstimulated peritoneal macrophages, but was observed when 'activated' peritoneal exudate cells were tested. These data are discussed in terms of a two-cell model for suppression of blastogenesis, the ultimate effector cell being a macrophage, the activity of which is controlled by a long-lived, recirculating lymphocyte, which we have provisionally designated as a T lymphocyte.

Aging↗
PubMed1980

Fixation and staining of granules in mucosal mast cells and intraepithelial lymphocytes in the rat jejunum, with special reference to the relationship between the acid glycosaminoglycans in the two cell types.

Various fixation and staining procedures have been examined in order to obtain optimal numbers and acceptable morphology of the mucosal mast cells and granular intraepithelial cells in the rat jejunum. For subsequent staining with Alcian Blue, the best fixation of the jejunum was obtained with a methanol-formaldehyde-acetic acid mixture. Specific staining of the granules of these cells has been obtained using Alcian Blue at pH 5.8, at which hydrogen ion concentration more cells stain than in the usual very acid conditions. Specificity is achieved by the use of magnesium chloride concentrations above the critical electrolyte concentrations for staining of protein and nucleic acid by Alcian Blue, and by the use of Safranin O as a competitive counterstain. The critical electrolyte concentration technique has also been applied to a comparative study of the glycosaminoglycan in the two cell types. Evidence is presented that the glycosaminoglycan in the granular intraepithelial cell has either a lower degree of sulphation or a lower molecular weight or both than the material in mucosal mast cells. This finding may support the possibility that the granular intraepithelial lymphocyte is a precursor of the mucosal mast cell.

Alcian Blue↗
PubMed1980

Thymus-dependent and thymus-independent subpopulations of intestinal intraepithelial lymphocytes: a granular subpopulation of probable bone marrow origin and relationship to mucosal mast cells.

Intraepithelial lymphocytes have been examined histochemically in the small intestines of normal rats and mice and in thymus-deficient animals (B rats and nude mice). It is concluded that these cells are heterogeneous, consisting of at least two subpopulations. One population contains granules, is thymus-independent, and is probably bone-marrow-derived. The other population does not contain granules and appears to be thymus-dependent. It is suggested that the granular cell, which may be a precursor of mucosal mast cells, is more properly a previously unrecognized nonlymphoid leukocyte of bone marrow origin.

Animals↗