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G G MacPherson

Publications and source records attributed to G G MacPherson.

At least 37 records · Page 2Linked to original sources
PubMed1990

Analysis of thymus-independent type 2 antigen uptake by marginal zone macrophages in thin slices of viable lymphoid tissue in vitro.

There is evidence to suggest that the B cell population in the marginal zone (MZ) of the spleen is responsible for the antibody response to thymus-independent type 2 antigens (TI-2). The macrophage (M phi) population in the MZ has been shown to take up TI-2 antigens selectively, and this uptake is potentially important in understanding antigen handling in TI-2 responses. Uptake has not been studied in vitro because isolation of MZ M phi completely abrogates uptake. We have adapted a technique for cutting thin slice of viable spleen which retained this M phi function under in vitro conditions and allowed manipulation of the system. This technique may have widespread application in the study of tissue M phi which are difficult to isolate. Using this method, we show that MZ M phi in splenic slices in vitro selectively take up a TI-2 antigen, in a way apparently identical to that seen in vivo. This is not due to high pinocytic activity by these cells nor to their anatomical location. We provide evidence for a receptor-mediated uptake system, whose function is sensitive to collagenase. The ligand specificity of the uptake system showed unexpected cross-reactivity with the mannosyl-fucosyl receptor with high affinity for mannan, but was not identical to it, and may be indicative of the natural ligands for the TI-2 antigen uptake system.

Animals↗
PubMed1989

Lymph node macrophage heterogeneity: the phenotypic and functional characterization of two distinct populations of macrophages from rat lymph node.

The isolation and characterization of lymph node macrophages (M phi) has shown a hitherto unknown heterogeneity. Two types of M phi were distinguished by morphology, monoclonal antibody staining and functional assays. The type I M phi failed to express surface Ia even when activated, a characteristic which has only previously been reported for splenic marginal zone M phi; despite studies suggesting an antigen presentation role for the M phi, the failure to express surface Ia would seem to eliminate an interaction with T helper cells for the type I M phi in the lymph node. In contrast, the type I M phi, other characteristics of clustering with activated B cells in vitro, the colocalization of the type I M phi and activated B cells in situ, the specific uptake of thymus-independent type 2 antigens and the failure to undergo respiratory burst activity all suggest a M phi-B cell interaction, possibly of a trophic nature. The defective microbicidal activity of the type I M phi may have been compensated for by the type II M phi, which expresses both strong respiratory burst activity and surface Ia expression when freshly isolated. However, unlike the inflammatory M phi the activated phenotype of the type II M phi did not appear to be interferon-gamma dependent because type II M phi could also be isolated from nude rat lymph nodes.

Animals↗
PubMed1989

Properties of lymph-borne (veiled) dendritic cells in culture. I. Modulation of phenotype, survival and function: partial dependence on GM-CSF.

Lymph-borne dendritic cells (L-DC) collected from the thoracic duct of rats following mesenteric lymphadenectomy are derived from the small intestine. We have cultured these cells in vitro and examined their survival and phenotypic and functional changes. L-DC survive poorly in culture in normal media (less than 50% overnight) but survival can be markedly increased by supplementation with Con A-stimulated spleen cell supernatant or recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) but not by recombinant IL-1, IL-2, IFN-gamma or by an IL-3-rich supernatant. The effects of GM-CSF are blocked by a specific antiserum. L-DC display heterogeneity for some surface markers, cytoplasmic inclusions and enzyme reactivity. After 16-48 hr culture the pattern of expression is markedly different. The numbers of Thy-1-positive L-DC and the amount of Thy-1 expressed increases, as do the numbers of L-DC expressing OX48 antigen. All L-DC remain Ia positive, but the proportion expressing the iC'3b receptor, non-specific esterase or cytoplasmic DNA inclusions decreases to almost zero. In contrast to Langerhans' cells, fresh L-DC are potent stimulators of an allogeneic mixed leucocyte reaction (MLR) but their potency is considerably increased after 16 hr culture. Also in contrast to Langerhans' cells, the increase in potency is not affected by culture with CAS and is thus unlikely to be dependent on GM-CSF. The changes described in L-DC properties could be related to their role as antigen-presenting cells.

Animals↗
PubMed1989

Properties of lymph-borne (veiled) dendritic cells in culture. II. Expression of the IL-2 receptor: role of GM-CSF.

Fresh lymph-borne (veiled) dendritic cells (L-DC) in the rat are almost totally negative for the interleukin-2 (IL-2) receptor detected by the monoclonal antibody (mAb) MRC OX39. After 16 hr culture more than 90% of L-DC are OX39 positive, and increased levels of expression can be seen within 5 hr culture. In cultures of L-DC and allogeneic lymphocytes. L-DC appear to express the IL-2 receptor more rapidly than lymphocytes. The intensity of labelling of L-DC is variable but maximal levels are similar to those seen on lymphoblasts. Culture in the presence of concanavalin A (Con A)-stimulated spleen cell supernatants or recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) results in a more rapid and intense expression of the IL-2 receptor by L-DC. L-DC cultured following rigorous T-cell depletion, or derived from athymic rats also express the IL-2 receptor after culture with GM-CSF. Cultured, but not fresh, L-DC bind iodinated recombinant IL-2 in a dose-dependent manner and binding is inhibited by excess unlabelled ligand. The amount of IL-2 bound varies but maximal amounts are similar to those bound by lymphoblasts. Following intravenous endotoxin injection, a large proportion of freshly collected L-DC express the IL-2 receptor and the number of L-DC released into the lymph is increased. An antibody to the IL-2 receptor which blocks an allogeneic MLR has no effect on a xenogeneic MLR using rat L-DC as stimulators and mouse lymphocytes as responders.

Animals↗
PubMed1988

Lymph node macrophage heterogeneity: a subpopulation fails to express activation phenotype.

We have identified and characterised a subpopulation of macrophages in the rat lymph node. The stromal macrophage shows many characteristics not expressed by peritoneal macrophages; clustering of B cells, selective uptake of TI-2 antigens, failure to express surface Ia after activation. These differences are suggestive of a regulatory role in B cell rather than T cell function.

Animals↗
PubMed1987

Expression of the W6/32 HLA epitope by cells of rat, mouse, human and other species: critical dependence on the interaction of specific MHC heavy chains with human or bovine beta 2-microglobulin.

The HLA class I epitope W6/32 is conformationally dependent on both heavy chain and beta 2-microglobulin (beta 2M). Previously, the W6/32 epitope has been detected in humans and other primates as well as from bovine sources. Two controversial reports suggest the W6/32 epitope is constitutively expressed by either normal or transformed murine cells expressing the Db allele. Here we show that the appearance of the W6/32 epitope in murine cells results from the association of either the Db or Kd gene products with either bovine or human beta 2M. We use congenic mouse strains and hybrid H-2 class I genes between Db and Kb to map the W6/32 epitope to particular amino acid residues in the alpha 2 domain. Subsequently, we show that beta 2M exchange is not confined to murine or human cells in vitro but can be detected after beta 2M injection into a mouse. The data presented suggests that beta 2M exchange takes place at the cell surface under physiological conditions and indicates that MHC class I heavy chains are in an equilibrium between the bound and unbound form of beta 2M.

Amino Acid Sequence↗
PubMed1986

Endotoxin-mediated necrosis and regression of established tumours in the mouse. A correlative study of quantitative changes in blood flow and ultrastructural morphology.

The fractional distribution of cardia output was measured in tumour-bearing mice treated with 50 micrograms intravenous endotoxin, and correlated with ultrastructural changes in tumour morphology. The proportion of the cardiac output going to the tumour decreased to less than 50% of its original value by 2 h and to 10%-30% by 6 h after giving endotoxin. Because endotoxin decreases absolute cardiac output, the actual perfusion of the tumour will be considerably less than these figures suggest. The decrease in perfusion correlated closely with changes in vascular morphology. Venous congestion on the tumour edge started within 1 h of giving endotoxin and by 3 h, endothelial damage and platelet aggregates were visible. At this time, all cells, tumour, connective tissue and infiltrate in the tumour centre were dead or damaged. By 24-48 h a conspicuous infiltrate of neutrophils and macrophages was present on the edge of the tumour and many of these cells were closely related to tumour cells. We suggest that the haemorrhagic necrosis may be caused by vascular obstruction leading to hypoxia and that the subsequent regression is mediated by activated macrophages and perhaps by neutrophils.

Animals↗
PubMed1985

Interaction of human monocytes, macrophages, and polymorphonuclear leukocytes with zymosan in vitro. Role of type 3 complement receptors and macrophage-derived complement.

Macrophages take up zymosan in the absence of exogenous complement via receptors for iC3b (type 3 complement receptors) acting with or without lectin-like receptors for mannosyl-fucosyl-terminated glycoconjugates. We previously provided evidence that macrophages themselves secrete complement-alternative pathway components able to opsonize zymosan locally (Ezekowitz et al., J. Exp. Med. 1984. 159:244-260). We show here that covalently bound C3 cleavage products C3b and iC3b can be eluted from zymosan particles cultivated with 36-h adherent human monocytes in the absence of serum. The ligand binding site of type 3 complement receptors is involved in macrophage-zymosan interactions as shown by inhibition studies of zymosan binding and uptake with Fab fragments of anti-C3 antibodies and monoclonal antireceptor antibodies M01 and OKM10. In contrast, antibody IB4, which binds to a receptor epitope distinct from the binding site, does not inhibit zymosan uptake. Selective modulation of macrophage receptors onto anticomplement receptor antibody and mannose-rich yeast mannan, respectively, confirms that the complement and lectin-like receptors are distinct. Human polymorphonuclear leukocytes, which express receptors for complement, but are not known to secrete complement proteins, bind and ingest only exogenously opsonized zymosan. Unopsonized zymosan is a poor trigger of respiratory burst activity in neutrophils or 7-d adherent human macrophages, but induces cell aggregation and secretion of large amounts of superoxide anion when these cells are co-cultivated in serum-free medium and challenged with zymosan. Our studies indicate that complement and/or other products synthesized by macrophages at extravascular sites could play an important role in opsonization and lysis of pathogens able to activate the alternative pathway and mediate macrophage-neutrophil collaboration in first-line host defence.

Animals↗
PubMed1985

Human cerebral malaria. A quantitative ultrastructural analysis of parasitized erythrocyte sequestration.

For investigation of the pathogenesis of cerebral malaria, immediate postmortem samples from brain and other tissues of patients dying with Plasmodium falciparum malaria, with (CM) or without (NCM) cerebral malaria, were processed for electron microscopy. Counts of parasitized erythrocytes (PRBCs) in cerebral and other vessels showed that the proportion of PRBCs was higher in CM than in NCM, and also that the proportion of PRBCs was higher in the brain than in other organs examined in both CM and NCM. Cerebral vessels from CM patients were more tightly packed with RBCs than those from NCM patients, but there was no significant difference in the amount or degree of endothelial damage or numbers of vessels with endothelial pseudopodia. Fibrillar (fibrin) deposits were present in a small proportion of vessels, but no thrombosis was present. There was neither acute nor chronic inflammation, and leukocytes were absent within or outside cerebral vessels. There was no immune complex deposition in cerebral vessels. Parasites in cerebral vessels were mainly trophozoites or schizonts. Occasional RBC remnants following parasite release were seen. Some parasites were degenerate, resembling crisis forms. PRBCs adhered to endothelium via surface knobs. It is concluded that there is no evidence for an inflammatory or immune pathogenesis for human cerebral malaria and that the clinical effects probably relate to anoxia and the metabolic activities of the parasites.

Adolescent↗
PubMed1984

Heterogeneity amongst lymph-borne "dendritic" cells.

Thoracic duct lymph from mesenteric lymphadenectomized rats contains a population of non-lymphocytic, irregularly shaped, Ia-positive cells. These cells are able to stimulate an allogeneic or syngeneic MLR, can act as accessory cells in Concanavalin A-induced lymphocyte mitogenesis and can stimulate the rejection of enhanced allografts. They are thus similar to dendritic cells isolated from lymphoid and peripheral tissues. These cells are not endocytic or glass adherent and do not bear C3 receptors or mannose-fucose receptors. They may possess weak Fc receptor activity. In terms of morphology, cytochemistry and surface markers these cells show marked heterogeneity. The nature of this heterogeneity is described and the relationship of these cells to other potential accessory cells is discussed in terms of lineage and function.

Animals↗
PubMed1984

The role of the macrophage in cardiac allograft rejection in the rat.

Macrophages (MO) are a well-recognized component of the cellular infiltrate in first-set (acute) allograft rejections. Definition of their actual role in the mediation of rejection depends on showing that they are present in sufficient numbers and at relevant sites in rejecting grafts, that they are capable of mediating damage to graft tissues, and that their absence interfere with rejection. We have used rat heart allografts to investigate these questions. Normal rejection takes 7 days. By this time the MO is the major infiltrating cell and large numbers are present close to myocardial cells. In some cases they appear to push pseudopodia into the cell. Neither they, or other cell types, appear to be interacting with endothelial cells. MO extracted from rejecting allografts are potent secretors of plasminogen activator but show poor glass adherence and phagocytic ability compared to resident peritoneal cells. Graft MO are able to damage beating heart cells in vitro; their activity is not immunologically specific. Peritoneal MO from rats immunised with allogeneic spleen cells and MO grown in vitro from bone marrow in the absence of allostimulators behave similarly. Manipulation of MO behaviour was attempted with rabbit anti-rat MO serum. This did not prolong allograft survival and did not significantly depress blood monocyte levels. 750 rads irradiation prolonged graft survival usually until the death of the animal. Rejection could be restored with small lymphocytes from a normal rat, and the addition of bone-marrow cells had no effect. However, hearts rejected by animals given irradiation and lymphocytes alone contained as many MO as those rejected by normal animals, despite a reduction in blood monocyte levels to less than 5% of normal. We conclude that MO are present in large numbers and at relevant sites in rejecting allografts, and that they show features of activation and have a cytotoxic capability against relevant target cells. However, present approaches available for the prevention of MO accumulation in rejecting allografts are inadequate and, thus, no definitive statements about the need for MO as an effector cell in allograft rejection can be made.

Animals↗
PubMed1983

The mononuclear phagocyte system of the mouse defined by immunohistochemical localization of antigen F4/80. Relationship between macrophages, Langerhans cells, reticular cells, and dendritic cells in lymphoid and hematopoietic organs.

The macrophage-specific antigen F4/80 has been localized in mouse lymphoid and hematopoietic tissue and skin using immunoperoxidase staining. The antigen permits identification of early mononuclear phagocyte precursors in the bone marrow, and is present also on larger cells forming the center of hematopoietic islands and lining vascular sinuses. In thymus F4/80+ cells are numerous in both cortex and medulla and are particularly concentrated around the corticomedullary region. In spleen, lymph node, and gut-associated lymphoid areas the major F4/80+ populations are in the red pulp, the medulla and subcapsular sinus, and the adjacent lamina propria, respectively. F4/80+ cells are rarely seen in T-dependent areas of lymph nodes, spleen, or Peyer's patch, but are present in large numbers in these areas during bacillus Calmette-Guerin (BCG)-induced inflammation. Macrophage infiltration occurs also in lymph nodes from athymic nu/nu mice and is therefore T cell independent. The interdigitating cell of T-dependent areas is F4/80-, but the Langerhans cell of the epidermis of the skin, which bears some ultrastructural resemblance to the interdigitating cell, is F4/80+. We conclude that the two cell types are probably not related.

Animals↗
PubMed1983

Characterization of nonlymphoid cells derived from rat peripheral lymph.

Mesenteric lymphadenectomy in rats is followed by union of peripheral and central lymphatics, allowing the collection of intestine-derived peripheral lymph cells via the thoracic duct for several days. These cells include a proportion of nonlymphoid cells (NLC) that show irregular and heterogeneous surface morphology including long pseudopodia and veils. They stain variably for nonspecific esterase and acid phosphatase and are ATPase-positive. Their nuclei are irregular and some contain cytoplasmic inclusions, some of which show peroxidase activity and/or contain DNA. NLC have a range of densitites generally lower than that of lymphocytes. Freshly collected NLC express the leukocyte-common antigen (defined by monoclonal antibody MRC Ox 1) and Ia antigens (I-A and I-E subregion products defined by monoclonal antibodies) but they show a relative lack of other surface markers normally found on rat B or T lymphocytes (W3/13, W3/25, MRC Ox 12 (sIg), MRC Ox 19) or rat macrophages (FcR, C'R, mannose R, W3/25). In general NLC are only weakly adherent to glass or plastic. Although a subpopulation of NLC appear to have had a phagocytic past, freshly collected NLC fail to phagocytose a variety of test particles in vitro. NLC also appear incapable of pinocytosis in vitro. This heterogeneity may represent distinct subpopulations of NLC or different stages in the development of a single cell lineage. Direct cannulation of mesenteric lacteals shows that the majority of NLC are derived from the small intestine and their precursors appear to be present both in lamina propria and Peyer's patches. Kinetic studies, following irradiation or intravenous tritiated thymidine, show that the majority of NLC turn over rapidly in the intestine with a modal time of 3-5 d. Studies with bone marrow chimeras show that they are derived from a rapidly dividing precursor present in normal bone marrow. NLC occur at very low frequencies in normal thoracic duct lymph at all times following cannulation. The evidence presented suggests that NLC closely resemble mouse lymphoid dendritic cells. This conclusion is supported by evidence already obtained showing that NLC are potent stimulators of the semi-allogeneic rat primary mixed leukocyte reaction. In addition to the ceils resembling dendritic cells rare monocytoid cells are found in thoracic duct lymph of lymphadenectomized specific pathogen-free rats. The proportion of these cells increases greatly when the animals are conventionally housed. It seems probable that the physiological function of NLC is to act as accessory cells in the lymph nodes to which they normally drain. Methods for enriching NLC and thus facilitating analysis of their functions are discussed.

Animals↗