An in vivo mammary infusion model for tissue migration of leucocytes during inflammation

Adaptive Cell-Mediated Immunity in the Mammary Gland of Dairy Ruminants

Mastitis is one of the greatest issues for the global dairy industry and controlling these infections by vaccination is a long-sought ambition that has remained unfulfilled so far. In fact, gaps in knowledge of cell-mediated immunity in the mammary gland (MG) have hampered progress in the rational design of immunization strategies targeting this organ, as current mastitis vaccines are unable to elicit a strong protective immunity. The objectives of this article are, from a comprehensive and critical review of available literature, to identify what characterizes adaptive immunity in the MG of ruminants, and to derive from this analysis research directions for the design of an optimal vaccination strategy. A peculiarity of the MG of ruminants is that it does not belong to the common mucosal immune system that links the gut immune system to the MG of rodents, swine or humans. Indeed, the MG of ruminants is not seeded by lymphocytes educated in mucosal epithelia of the digestive or respiratory tracts, because the mammary tissue does not express the vascular addressins and chemokines that would allow the homing of memory T cells. However, it is possible to elicit an adaptive immune response in the MG of ruminants by local immunization because the mammary tissue is provided with antigen-presenting cells and is linked to systemic mechanisms. The optimal immune response is obtained by luminal exposure to antigens in a non-lactating MG. The mammary gland can be sensitized to antigens so that a local recall elicits neutrophilic inflammation and enhanced defenses locally, resulting from the activation of resident memory lymphocytes producing IFN-γ and/or IL-17 in the mammary tissue. The rational exploitation of this immunity by vaccination will need a better understanding of MG cell-mediated immunity. The phenotypic and functional characterization of mammary antigen-presenting cells and memory T cells are amongst research priorities. Based on current knowledge, rekindling research on the immune cells that populate the healthy, infected, or immunized MG appears to be a most promising approach to designing efficacious mastitis vaccines.

Production of monoclonal antibodies reactive with ovine eosinophils

BACKGROUND

There is strong evidence implicating eosinophils in host defence against parasites as well as allergic disease pathologies. However, a lack of reagents such as monoclonal antibodies (mAbs) specific for eosinophils has made it difficult to confirm the functional role of eosinophils in such disease conditions. Using an established mammary model of allergic inflammation in sheep, large numbers of inflammatory cells enriched for eosinophils were collected from parasite-stimulated mammary glands and used for the generation of mAbs against ovine eosinophils.

RESULTS

A panel of mAbs was raised against ovine eosinophils of which two were shown to be highly specific for eosinophils. The reactivity of mAbs 3.252 and 1.2 identified eosinophils from various cell and tissue preparations with no detectable reactivity on cells of myeloid or lymphoid lineage, tissue mast cells, dendritic cells, epithelial cells or other connective tissues. Two other mAbs generated in this study (mAbs 4.4 and 4.10) were found to have reactivity for both eosinophils and neutrophils.

CONCLUSION

This study describes the production of new reagents to identify eosinophils (as well as granulocytes) in sheep that will be useful in studying the role of eosinophils in disease pathologies in parasite and allergy models.

Lymphocyte migration studies

For maintenance of immunity and tolerance, the organs and tissues of the organism are connected by migrating lymphoid cells. Understanding lymphocyte migration is essential for many disorders and diseases-- especially in the mucosa-lined organs. Detailed analyses of migrating lymphocytes have been performed in many species, especially in laboratory animals. However, important experiments in lymphocyte migration have been carried out in large animals, for example sheep, cattle and pigs. These species allow experimental procedures like in situ-organ labelling, lymphocyte retransfusion studies or lymph vessel cannulations. Such studies have made an important contribution to the understanding of the overall principles of lymphocyte migration especially in the mucosal immune system. Major results on the specific migration of naïve and memory T cells through lymphoid organs, the re-distribution of gamma/delta T cells in the intestinal immune system and the emigration of newly produced B cells from the ileal Peyer's patches have been obtained in large animals. Since there are growing numbers of markers for large animals, and molecular biology methods are available in these species, experiments in large animals will be an essential tool for the understanding of lymphocyte migration especially in mucosal organs.

Isolation and characterization of a novel eosinophil-specific galectin released into the lungs in response to allergen challenge

A novel galectin cDNA (galectin-14) was cloned from ovine eosinophil-rich leukocytes by low stringency reverse transcriptase-PCR and cDNA library screening. Data base searches indicate that this gene encodes a novel prototype galectin that contains one putative carbohydrate recognition domain and exhibits most identity to galectin-9/ecalectin, a potent eosinophil chemoattractant. The sugar binding properties of the recombinant molecule were confirmed by a hemagglutination assay and lactose inhibition. The mRNA and protein of galectin-14 are expressed at high levels in eosinophil-rich cell populations. Flow cytometry and cytospot staining demonstrate that the protein localizes to the cytoplasmic, but not the granular, compartment of eosinophils. In contrast, galectin-14 mRNA and protein were not detected in neutrophils, macrophages, or lymphocytes. Western blot analysis of bronchoalveolar lavage fluid indicates that galectin-14 is released from eosinophils into the lumen of the lungs after challenge with house dust mite allergen. The restricted expression of this novel galectin to eosinophils and its release into the lumen of the lung in a sheep asthma model indicates that it may play an important role in eosinophil function and allergic inflammation.

Cellular kinetics of an allergic-type response in a sheep mammary gland model of inflammation

BACKGROUND

Tissue recruitment of eosinophils and activated lymphocytes is a characteristic feature of allergic reactions. However, little is known about the involvement of specific adhesion molecules in the traffic of leucocytes during the allergic response.

OBJECTIVE

To use a sheep mammary infusion model to characterize the kinetics of cell recruitment and expression of cellular adhesion molecules and activation markers on eosinophils and lymphocytes involved in an allergic-type response.

METHODS

Mature non-lactating ewes were primed and challenged by direct infusion of the mammary glands with nematode larvae. Using a non-invasive method of saline infusion and 'milking' of the glands, large numbers of inflammatory cells were repeatedly sampled over 10 to 96 h following their migration into the mammary gland lumen, and analyzed by 2-colour flow cytometry.

RESULTS

Leucocyte recruitment into the mammary lumen was characterized by two separate phases involving an acute neutrophilic response at 10 h post-challenge, followed by a dramatic reduction in neutrophils and appearance of eosinophils and activated lymphocytes. From 48 h post-challenge, eosinophils were predominant and represented 40 to 65% of leucocytes in the mammary lavage (MAL). Increases in activated CD4+ T cells and gammadelta+ T cells were also observed at this time-point. The kinetics of expression of cell surface molecules on eosinophils and lymphocytes in blood and MAL were compared during the course of the allergic-type reaction. Adhesion molecule expression on lymphocytes was modulated following allergen challenge and an activation of MAL vs. blood lymphocytes was seen during the later stages of the allergic response. Eosinophil expression of VLA-4 and l-selectin was down-regulated compared with blood at all time-points examined. There were high levels of expression of CD11b and CD44 on eosinophils during the early compared to the late-phase of the allergic reaction.

CONCLUSION

These results indicate the existence of two separate mechanisms of eosinophil recruitment during the allergic inflammatory response.

Expression of cell surface adhesion molecules by peripheral blood eosinophils during Trichostrongylus colubriformis infection in sheep

The effect of infection of sheep with the gastrointestinal nematode parasite Trichostrongylus colubriformis on expression of adhesion molecules CD11a, CD11b, CD11c, CD18, CD44, CD49d and CD62L by peripheral blood eosinophils was examined by flow cytometry. Initially, to establish the sensitivity of adhesion molecules to inflammatory signals, eosinophil-rich exudates were elicited in non-lactating mammary glands of immune sheep by infusion of 50 microg of soluble antigen extract from T. colubriformis third stage larvae. Eosinophils comprised 40.8% of mammary leucocytes and 4.5% of peripheral blood leucocytes. In comparison with blood, the percentage of eosinophils expressing CD18 increased and the percentage expressing CD62L decreased in exudates and the mean fluorescent intensity, an indicator of receptor number per cell, for CD11a and CD49d also decreased on exudate eosinophils. Peripheral blood eosinophils were examined over 8 weeks during trickle infection of immune sheep with infective or irradiated third stage larvae of T. colubriformis. During the last 3 weeks of infection, CD11a staining decreased in infected sheep and CD44 staining decreased in sheep receiving either infective or irradiated larvae. Other surface markers did not change. The results indicate that systemic changes in expression of adhesion molecules by eosinophils occur during T. colubriformis infection in sheep.

Isolation and characterization of a novel inducible mammalian galectin

A novel mammalian galectin cDNA (ovgal11) was isolated by representational difference analysis from sheep stomach (abomasal) tissue infected with the nematode parasite, Haemonchus contortus. The mRNA is greatly up-regulated in helminth larval infected gastrointestinal tissue subject to inflammation and eosinophil infiltration. Immunohistological analysis indicates that the protein is localized in the cytoplasm and nucleus of upper epithelial cells of the gastrointestinal tract. The protein is also detected in mucus samples collected from infected abomasum but not from uninfected tissue. The restricted and inducible expression of ovgal11 mRNA and limited secretion of the protein support the hypothesis that OVGAL11 may be involved in gastrointestinal immune/inflammatory responses and possibly protection against infection.

The intramammary inflammatory response of genetically resistant Merino ewes infected with Haemonchus contortus

The mammary glands of 103 pasture-reared non-lactating, non-pregnant Merino ewes were infused via the teat canal with antigens prepared from the nematode Haemonchus contortus, and the inflammatory response to infusion assessed by washing the gland of its contents after 24 h and 14 days. The ewes were of two genotypes: one with proven high levels of resistance to infection with the nematode H. contortus, the other random-bred animals with relative susceptibility to infection. On day 0 of a H. contortus infection, one gland of the subgroups of both genotypes was infused with the antigen preparation. At the same time, the other gland of the random-bred ewes was infused with sterile physiological saline. A third group of infected random-bred ewes was infused with only sterile physiological saline. Similar infusions were performed on other subgroups on days 12, 21 and 35 of infection, which was then terminated with anthelmintic. A fourth group of uninfected random-bred control ewes was given both infusions 35 days after the other groups were infected. Sheep of the resistant genotype had lower worm egg counts and smaller reductions in blood packed cell volumes from day 21 of infection. Infusion of antigen had no effect on the course of infection and no effect on the response of the other gland, which had been infused with saline alone. The dominant leukocyte response from the antigen-infused gland was eosinophilia. On all days of infusion, and after both 24 h and 14 days, eosinophil counts from the resistant genotype were higher than those from their random-bred counterparts. The sheep mammary gland provides a source of eosinophils whose number is related to host genotype and stage of infection and may provide a model for the investigation of cellular responses in mucosal immunity to nematode infections.