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Biomedical subjects

H Salmon

Publications and source records attributed to H Salmon.

At least 19 recordsLinked to original sources
PubMed2000

Mammary gland immunology and neonate protection in pigs. Homing of lymphocytes into the MG.

Since placenta of pregnant sows are impermeable to immunoglobulin passage, the neonates are born agammaglobulinemic; although immunocompetent, they are unable to develop rapidly an immune response which will protect their systemic and mucosal compartments; thus their survival depend upon the passive acquisition of maternal immunity including at least 3 components: i) a systemic humoral immunity, transmitted through colostrum conveying mainly by IgG; these IgG are transferred from maternal serum via Fc gamma receptors on the epithelial cells of mammary gland (MG). ii) a local humoral immunity, especially secretory IgA (IgAs), transmitted mainly by milk (lactogenic immunity) until weaning. IgAs are secreted by MG recruited plasma cells and are excreted in milk via secretory component of epithelial cells: these IgA exhibit a specificity for the antigens present in the maternal digestive tract, the so-called "entero-mammary link"; this link is due to the migration of lymphocytes from the gut to the mammary gland; they are recruited from the blood via the interaction of their homing receptor (alpha 4 beta 7) with the developmentally regulated mucosal vascular addresin MadCAM-1. In the MG, MadCAM-1 increased in pregnancy (probably under oestrogenic stimulation) but regressed in lactation; its density is closely related to the T cell numbers in MG; in contrast the increase in plasma cell numbers is not related to MadCAM-1 density. Thus IgA precursor cells (alpha 4 beta 7 B cells) seem to be recruited by a milk B cell chemoattractant. On the other hand, presence of T and B lymphocytes in MG (some of them originating from the systemic compartment), sustains the attempts of MG immunization and the results sustain the view of a true local immune response. iii) possibly but not formally proved, a cellular immunity transmitted via maternal immunocompetent cells present in mammary secretions; the exported lymphocytes may represent a selected population of lymphocytes after their passage through the MG epithelium.

Animals↗
PubMed2000

Dendritic cells enriched from swine thymus co-express CD1, CD2 and major histocompatibility complex class II and actively stimulate alloreactive T lymphocytes.

Initial characterization and partial purification of thymic dendritic cells (DC) from miniature swine were carried out with the ultimate goal of using these cells to induce transplantation tolerance in this preclinical animal model. Immunohistochemical analysis of swine thymic tissue sections has shown DC to be large cells located in the medullary and the cortico-medullary regions as evidenced by the presence of surrounding Hassal bodies. These cells exhibit membrane processes and express the CD1, granulocyte/macrophage (G/M), and major histocompatibility complex (MHC) class II surface antigens, as well as the S100 cytosolic and nuclear markers found in humans to be specific for DC. Dendritic cells were purified from thymi following collagenase treatment, Percoll gradient centrifugation, and adhesion steps to plastic. Cells similar in morphology and phenotype to those described in tissue sections were detected in the lighter density layers of the gradient and represented 0.02% of the starting cell number. Removal of plastic nonadherent cells showed enrichment levels similar to those reported for murine and human DC. Two-colour flow cytometric analysis of purified pig DC identified these cells as MHC class IIhi, CD1+, CD2+, and G/M+. The dendritic nature of these cells was confirmed by their potent ability to stimulate alloreactive T lymphocytes. Modification of porcine thymic DC by transfer of allogeneic MHC genes and reinjection into the DC donor should permit testing of the role of this DC subset in the induction of transplantation tolerance.

Animals↗
PubMed2000

Development of an ex vivo model of pig kidney perfused with human lymphocytes. Analysis of xenogeneic cellular reactions.

BACKGROUND: Because of the explosive nature and the extremely rapid process of hyperacute rejection (HAR), significant infiltration of the xenograft by immunocompetent cells is not observed, and the role and the mechanism of action of cell-mediated rejection in discordant xenografts are therefore still under discussion. METHOD: We developed an experimental approach using pig kidneys perfused with human peripheral blood lymphocytes (PBL) in which the immunologic barrier of hyperacute rejection was excluded and which mimics the in vivo situation. RESULTS: PBL retention in the kidney was evaluated at 20-minute intervals for 3 hours. Retention increased from 30% to 80% with the time of perfusion and was specific because significantly fewer syngeneic lymphocytes were retained. Phenotype analysis of recovered PBL showed a significant decrease in natural killer (NK) cells. Immunohistochemical studies revealed the presence of NK cells and T lymphocytes in the glomerular and interstitial tubular structures of the kidney. Functional studies showed a progressive cessation of diuresis and augmentation of renal vascular resistance when the kidney was perfused with PBL. Electron microscopy examinations of kidney sections perfused with PBL showed swollen endothelial zones, suggesting alterations to and damage of the endothelium. CONCLUSIONS: This system provides a valuable model for the study of early discordant xenogeneic cellular rejection and demonstrates the predominance of xenograft infiltration by NK cells.

Animals↗
PubMed2000

Fetal target organs of graft-versus-host reaction induced in utero by injection of maternal cells in a pig model.

The target organs of graft-versus-host reaction (GVHR) in adult or neonates are the site of multifocal lymphocytic infiltrates. GVHR can also be acquired in utero by maternal cells crossing the placenta, but the fetal target organs are unknown. The aim of this study was to determine these target fetal organs. The distribution pathway of infused labeled lymphocytes within cryostat sections of fetal organs was analyzed, and fetal target organs of infused lymphocytes were investigated in both isogenic and semiallogenic situations. Isogenic cells were observed in less organs and semiallogenic cells were localized in a more restricted number of organs than isogenic cells. Furthermore, the liver, the thyroid, and the spleen were the fetal target organs in the two studied gestations. GALT, thymus, and kidney were also lymphocyte targets in isogenic gestation. In conclusion, isogenic cells induced GVHR in more fetal organs than semiallogenic cells.

Animals↗
PubMed1999

The mammary gland and neonate mucosal immunity.

The passive mucosal protection of neonate mammals is dependent on the continuous supply until weaning of maternally dimeric IgA (monogastric) and IgG1 (ruminants). This lactogenic (humoral) immunity is linked to the gut, the so-called entero-mammary link, because of the translocation of Ig (IgA and IgG1) or the emigration of IgA lymphoblasts from the gut into the mammary gland (MG); on the other hand, studies on the lymphocyte subsets in the MG of artiodactyls sustained the view of a true local immune response, depending on the MG stage development. Accordingly, the increase of the lactogenic immunity may focus on (1) inductor sites (gut and, possibly, the MG), (2) increase in cell traffic from the gut into the MG, and (3) enhancement at the effector site of the Ig production and excretion in milk. A specific mucosal environment (interleukins and hormones) is responsible for IgM/IgA switch, the induction of mucosal homing receptor onto lymphoblasts and mucosal vascular addressins; very few data are available for the mechanism of lymphoblasts recruitment, either IgA or IgG1, although lactogenic hormones have been implicated in the IgA-blasts homing into the mice MG. After weaning, the neonate is able to mount a gut immune response, but the shortage of the suckling period did not seem to be detrimental for its onset. In soyabean allergy, both piglet and calf exhibited gut villus atrophy, gut accumulation of IgA (swine) and IgG1 (cattle) immunocytes, sustaining the view that a specific environment in ruminant is responsible for both IgA and IgG1 production.

Animals↗
PubMed1999

The xenotransplantation of goat and human hematopoietic cells to sheep fetuses.

Hematopoietic xenografts were carried out in three experiments using goat fetal liver (44-48 days, experiments I and II) or purified human CD 34+ cells (experiment III) as the donor cells. Recipients were sheep fetuses at 41-47 days of gestation. Goat fetal liver cells were either injected without any pretreatment or stimulated by preincubation in a culturing in goat phytohemagglutinin-stimulated lymphocyte supernatant. Human CD 34+ myeloid progenitor cells were purified from bone marrow by minimacs immunomagnetic purification and cultured in medium supplemented with stem cell factor, IL3, and IL6. Goat-sheep chimerism was assessed by flow cytometry analysis (FCA) of peripheral blood and bone marrow cells using a mouse anti-goat CD 45 monoclonal antibody and by karyotype analysis of peripheral blood from goat/sheep chimeras. Human cell engraftment was assessed by polymerase chain reaction amplification of the human DAX1 gene in blood and bone marrow DNA from sheep which had received human cells. In the three experiments, a mean of 76% (26 of 34) of injected fetuses were born alive without any clinical evidence of graft-versus-host disease. Three lambs were found to be goat/sheep chimeric after flow cytometry analysis (peripheral blood and bone marrow) and karyotype (peripheral blood) analysis. Both tissues continued to express goat cells at 6 or 12 months (last assessment) depending on the experiment. No human chimerism was detected using polymerase chain reaction amplification in peripheral blood and bone marrow of any of the six sheep grafted with human cells. These data and those also obtained on other species (human, pig/sheep) show that it is possible to carry out hematopoietic xenografts using the sheep fetus as recipient provided both donor and recipient fetal cells are processed during the period of tolerance to foreign antigens.

Aging↗
PubMed1998

Effect of cryopreservation on chemotaxis of lymphocytes.

Cryopreservation of cells appears to be a potential method of comparing chemotaxis of lymphocytes collected from different anatomical sites at one time in a single assay. Migration of cryopreserved lymphocytes from swine in the absence (spontaneous migration) or presence of N-formyl-methionyl-leucyl-phenylalanine (fMLP, induced migration) was compared to that of fresh lymphocytes, originating from inguinal (ILN) and mesenteric (MLN) lymph nodes, respectively, using a 48-well microchemotaxis chamber. Cryopreservation did not affect the optimal concentration of fMLP for maximal induced migration and did not impair the chemoattractant activity of fMLP as shown by checkerboard assay. However, cryopreservation reduced the extent of fMLP-induced migration by affecting the spontaneous motility of cells, an effect which was greater for MLN than for ILN cells. This reduction was not related to a loss of cell subset and is in keeping with the view that spontaneous and induced migration involve distinct mechanisms. Thus cryopreservation may be of general use to study the migration of lymphocytes by reducing the differences in spontaneous migration of lymphocytes from different sites.

Blood Preservation↗
PubMed1996

Identification of soyabean allergens and immune mechanisms of dietary sensitivities in preruminant calves.

The allergenicity of soya proteins was assessed by direct skin testing and by in vitro lymphoproliferation tests in calves fed milk substitutes containing skim milk powder (SMP) or an antigenic heated soya flour (HSF). During the last three weeks of treatment, the calves were injected intradermally with raw soya flour (RSF), HSF, hydrolysed soya protein isolate (HSPI), SMP or purified soya proteins, after being premedicated with anti-histamine or not. Peripheral blood leucocytes (PBL) were grown over five days with various mitogens or dietary antigens, and the incorporation of tritiated thymidine was measured. Strong skin oedema reactions to RSF, HSF and all the purified proteins were observed in the calves fed HSF at various times up to 24 hours after injection. The skin oedema was largely prevented by premedication with anti-histamine. A strong delayed skin thickening was observed in the calves fed HSF for up to five days with beta-conglycinin. PBL from the calves fed HSF proliferated in vitro with HSF, HSPI and beta-conglycinin, but not with glycinin. Thus, most proteins from soyabean were implicated in the immediate and semi-delayed immune reactions, whereas beta-conglycinin was strongly involved in a delayed type hypersensitivity in calves.

Allergens↗
PubMed1995

Evidence of noninvolvement of swine MHC class II in the in vitro proliferative response of human lymphocytes to porcine endothelial cells.

Successful pig-to-human xenotransplantation may expose swine endothelium to the human immune system. Since endothelial MHC class II expression is crucial in the genesis of an allogeneic lymphocyte response, the involvement of porcine MHC (SLA) class II molecules in the induction of human lymphocyte proliferation was studied. When cocultured with a confluent monolayer of irradiated porcine aortic endothelial cells (PAEC), human peripheral blood mononuclear cells (PBMC) incorporated tritiated thymidine. Monocyte depletion strongly reduced the magnitude of the lymphocyte proliferative response. Resting cultured PAEC were SLA class II-negative and an induction of these molecules during the xenogeneic mixed lymphocyte endothelial cell culture (XMLEC) was not observed. Moreover, the addition of an antibody directed against the SLA-DR molecule was without effect. Lymphocyte proliferation was also studied in response to SLA class II-positive stimulating cells--either human TNF-alpha-stimulated PAEC or porcine splenocytes. Induction of SLA class II molecules on PAEC had no effect on the human PBMC proliferative response. Moreover, human PBMC did not proliferate in response to porcine splenocytes. These results suggest (1) that SLA class II molecules are not involved in the induction of the human lymphocyte proliferative response and (2) that the endothelial nature of the stimulating cells plays a key role in this proliferation.

Animals↗
PubMed1995

IgM, IgA, IgG1 and IgG2 specific responses in blood and gut secretion of calves fed soyabean products.

Calves fed soya proteins may develop severe gastrointestinal disorders. Whether these are predominantly associated with particular Ig subclasses and (or) dietary proteins remains unclear. Therefore, antibody responses to soyabean protein were analysed by dot- and blot-immunobinding in plasma and intestinal mucous secretions. One-month-old calves were fed for 2.5 months liquid diets based on skim milk powder (SMP) or a mixture (2:3, protein basis) of whey and soyabean products including a low antigenic hydrolysed soya protein isolate (HSPI) and a highly antigenic heated soya flour (HSF). Specific antibodies (Abs) of the main isotypes (IgM, IgA, IgG1, IgG2) were characterised by immunostaining of samples which had been previously incubated with nitrocellulose sheets coated with SMP, HSPI or HSF extracts. Plasma collected before feeding experimental diets showed very little specific Abs. By contrast, 2.5 months later, a three-fold increase (P < 0.05) in IgG1 and IgA titres against HSF antigens was observed in calves fed HSF compared with those fed the control or HSPI diet. IgG1 immunoblotting revealed many protein bands from soya in the molecular range of 22-32 and 38-42 kDa. Immunorecognition of specific proteins from SMP and HSPI remained low and similar among animal groups. Specific IgM, IgA and IgG1 titres against HSF, and to a lesser extent HSPI, were significantly higher (P < 0.05) in jejunal mucous secretion of calves fed HSF compared with other groups. Secretions from calves fed HSF bound to many soyabean proteins in the range of 17-23 and 26-38 kDa, with similar patterns for IgA and IgG1. By contrast, only weak bands were found for IgM and IgG2 in all groups of calves. Thus, calves fed antigenic HSF do present specific Abs including IgG1 and IgA isotypes, both systemically and locally. Therefore, IgG1 and (or) IgA rather than IgM and IgG2 Abs may be preferred for assessing the immunogenicity of soyabean products in calves. Interestingly, soyabean immunogenicity was drastically reduced by adequate proteolysis.

Animals↗
PubMed1995

B and T lymphocytes are enhanced in the gut of piglets fed heat-treated soyabean proteins.

Gut immune responses have been suspected in food hypersensitivity reactions such as those to soyabean proteins in early-weaned piglets. The present study examines the lymphoid cell subset distribution in piglets fed heat-treated (HTSP) or ethanol-treated soyabean proteins (ETSP). Duodenal cryosections of 4-week-old HTSP piglets (n = 10) and ETSP piglets (n = 8) were analysed for IgA, IgM, IgG1 and IgG2 positive cells, CD2, CD4, CD8, WC1 T cell positive antigens using immunohistochemical peroxidase reactions. Densities of IgM+ and IgA+ cells were three times and, IgG1+ and IgG2+ six times higher in the lamina propria of HTSP piglets compared with ETSP (P < 0.05). Increased CD2+ T cells were accounted for by a rise in both CD4+ and CD8+ T cell subsets in the lamina propria (P < 0.01) as well as in the epithelium of the duodenal mucosa of piglets fed HTSP. The density of the WC1+ T cell subset in the epithelium was significantly higher in HTSP than in ETSP piglets (P < 0.01). Immune reactions in the duodenal mucosa, involving both B and T lymphocytes may be related to atrophy of the duodenal villi in HTSP piglets.

Animals↗