Expression of adhesion molecules on milk and blood lymphocytes from periparturient dairy cattle with Johne’s disease

Flow Cytometry Approach to Quantify the Viability of Milk Somatic Cell Counts after Various Physico-Chemical Treatments

Flow cytometry has been used as a routine method to count somatic cells in milk, and to ascertain udder health and milk quality. However, few studies investigate the viability of somatic cells and even fewer at a subpopulation level to follow up how the cells can resist to various stresses that can be encountered during technological processes. To address this issue, a flow cytometry approach was used to simultaneously identify cell types of bovine milk using cell-specific antibodies and to measure the cell viability among the identified subpopulations by using a live/dead cell viability kit. Confirmation of the cell viability was performed by using conventional microscopy. Different physico-chemical treatments were carried out on standardized cell samples, such as heat treatment, various centrifugation rates and storage in milk or in PBS pH 7.4 for three days. Cytometry gating strategy was developed by using blood cell samples stored at 4°C in PBS and milk cell samples heat-treated at 80°C for 30 min as a control for the maximum (95.9%) and minimum (0.7%) values of cell viability respectively. Cell viability in the initial samples was 39.5% for all cells and varied for each cell population from 26.7% for PMNs, to 32.6% for macrophages, and 58.3% for lymphocytes. Regarding the physico-chemical treatments applied, somatic cells did not sustain heat treatment at 60°C and 80°C in contrast to changes in centrifugation rates, for which only the higher level, i.e. 5000×g led to a cell viability decrease, down to 9.4%, but no significant changes within the cell subpopulation distribution were observed. Finally, the somatic cells were better preserved in milk after 72h storage, in particular PMNs, that maintained a viability of 34.0 ± 2.9% compared to 4.9±1.9% in PBS, while there was almost no changes for macrophages (41.7 ± 5.7% in milk vs 31.2 ± 2.4% in PBS) and lymphocytes (25.3 ± 3.0% in milk vs 11.4 ± 3.1% in PBS). This study provides a new array to better understand milk cell biology and to establish the relationship between the cell viability and the release of their endogenous enzymes in dairy matrix.

The CD markers of camel (Camelus dromedarius) milk cells during mastitis: the LPAM-1 expression is an indication of possible mucosal nature of the cellular trafficking

Studying the cellular populations of the camel mammary glands through the expression pattern of the CD markers and adhesion molecules is a mean to define whether the cellular trafficking pathway is peripheral or mucosal nature. Camel milk cells from 8 Gram-positive and 5 Gram-negative infected camels were examined with flow cytometry using cross-reacting antibodies like, anti-CD4(+), CD8(+), WC+1(+)γδ, CD62L, CD11a(+)/CD18, LPAM-1, CXCR2. The overall results indicated high flow cytometry output of most of the CD makers. The statistical analysis of the mean percentage of the expressed CD markers has shown that CD62L, CXCR-2, LPAM-1, CD11a/CD18, CD8(+), IL-6R and CD20(+) were expressed in significant differences in either type of the infection. The LPAM-1 expression has provided further support to the notion that the lymphocyte trafficking is of the mucosal nature. The mucosal origin of cellular trafficking has important implications on the vaccine design and therapeutical approaches to mastitis.

Vaccines against bovine mastitis in the New Zealand context: what is the best way forward?

Mastitis is an important animal health disease which constitutes a serious problem for the dairy industry in New Zealand. Mastitis reduces milk yield and quality, necessitates the use of antibiotic therapy, with associated risks of contaminating the raw milk supply, and imposes a serious economic burden, currently estimated at NZ$300 million per year. Mastitis is caused by a variety of infectious agents. In the New Zealand context, with cattle grazing on pasture, Streptococcus uberis is a major bacterial pathogen, responsible for a significant proportion of clinical cases, especially during early lactation and the dry period. Other pathogens of significance include Staphylococcus aureus, Streptococcus dysgalactiae and Escherichia coli, as well as so-called 'minor pathogens', namely coagulase-negative staphylococci(CNS). Current strategies aimed at reducing cases of mastitis include improved hygiene in the farm environment, particularly with regards to the health and cleanliness of teats. Once mastitis occurs, antibiotic therapy is a favoured option, and as a prophylactic tool, in the form of dry-cow therapy, has also shown value. Prevention of mastitis using immunological tools such as vaccines lags behind the major vaccine breakthroughs that have been achieved in preventing and/or reducing the severity of numerous infectious diseases in animals. In this review, the current state of research in the area of development of vaccines against mastitis is summarised, with particular emphasis on bacteria important to the dairy farming industry in New Zealand. Few, if any, effective vaccines have been designed to prevent or mitigate intramammary infections. It is argued that novel approaches must be considered to search for vaccine candidates, and vaccines need to be designed and constructed within the special framework of their uses, in the mammary gland which offers a unique immunological environment. In addition, effective vaccines against mastitis due to Strep. uberis may be more likely to emerge from strategies that target the cell-mediated arm of the immune response rather than strategies that target specific antibody responses.

Adhesion molecule expression in the bovine mammary gland

The bovine mammary gland requires lymphocytes for immune protection of the gland from foreign pathogens and, in addition, to transfer immune protection to the neonate via colostrum and milk. The process of homing primed lymphocytes to tissues is mediated by the interaction of cell-adhesion molecules displayed on the surface of lymphocytes and counter receptors displayed on the vascular endothelium. This study was conducted to identify the cell-adhesion molecules involved in homing lymphocytes to the bovine mammary gland at four different physiological stages; pregnant, colostral, lactation and involution. The expression and distribution of adhesion molecules in alveolar tissues and supramammary lymph nodes from the mammary glands of healthy cows was determined in situ by immunohistochemical analysis and compared with bovine Peyer's patch, used as a typical mucosal-associated lymphoid tissue and positive control. The mucosal addressin molecule, MAdCAM-1, was not detected in bovine mammary tissues at any of the four different physiological stages. Absence of MAdCAM-1 expression was verified by quantitative real-time RT-PCR analysis. Transcription levels of MAdCAM-1 mRNA were found to be more then 5 x 10(3)-fold lower in mammary alveolar tissues compared with bovine Peyer's patch tissues. In contrast to MAdCAM-1, phase-dependent protein expression of VCAM-1 was detected in both mammary alveolar tissues and the supramammary lymph nodes, with the highest expression observed in colostral phase cows. The protein expression in mammary alveolar tissues was limited to larger venules, although in colostral phase cows, VCAM-1 was also detected around the alveoli perimeter. In the supramammary lymph node, VCAM-1 protein was observed on both small and large venules. PNAd was detected in supramammary lymph nodes at all physiological stages of the mammary gland; however, it was not found in mammary alveolar tissues. Lymphocytes expressing beta7 were not detected in mammary tissues and lymphocytes expressing CD62L were only observed in the supramammary lymph nodes. Overall the data suggest that MAdCAM-1 and VCAM-1 are not involved in homing lymphocytes to the bovine mammary gland; whereas, VCAM-1 and PNAd may have this role in the supramammary lymph node.

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.

Changes Occurring in Immune Responsiveness of Single- and Twin-Bearing Comisana Ewes During the Transition Period

Changes induced by twin and single lambing in the immune response of 16 periparturient Comisana ewes were studied. Cell-mediated immune responses were evaluated by means of skin tests performed from 3 wk before and up to d 35 after parturition. At d 21 and 7 before lambing, the sheep received an intramuscular injection of the antigen keyhole limpet hemocyanin (KLH), to which the animals had not been previously exposed, to determine their humoral immune response. Starting 3 wk before lambing and up to d 35 postlambing, the ewes were sampled to determine the plasma concentrations of anti-KLH antibody (IgG), IL-6, and IL-1 beta. From parturition through d 35 postpartum, individual milk samples were collected for determination of anti-KLH IgG titers and IL-6 and IL-1beta concentrations by means of a capture ELISA. The number of lambs born affected IL-6 concentrations in ewe plasma; IL-6 secretion always was higher in ewes birthing twins than in single-lambing ewes. Apart from the number of lambs born, the concentrations of plasma IL-6 in ewes were higher at lambing than at d 21 antepartum and at d 35 postpartum. An interaction of number of lambs born x time of sampling was observed for plasma antibody titers to KLH. The IgG concentrations were significantly higher in single-bearing ewes than in twin-bearing ewes before parturition and were very similar across groups after parturition. A time effect was found for the cell-mediated immune response and for anti-KLH IgG concentrations in milk, such that at parturition, cellular responses were lowest, and the anti-KLH IgG concentration was highest. A significant correlation was found for IgG titers to KLH in plasma and milk. Results indicate that IL-6 concentrations in blood can be considered a reliable indicator of stress connected to lambing and that the mammary gland is a microenvironment unrelated to blood stream with respect to interleukins expression. In contrast, a relationship was found for the IgG secretions in milk and blood, which suggests that the assessment of humoral immune status may be combined with milking routine in dairy animals.

Expression of lymphocyte homing and adhesion molecules during intramammary infection of cows with Serratiamarcescens or Streptococcusuberis: correlation with bacterial colonization and clinical signs

We wished to determine the expression of trafficking/adhesion molecules on the surface of lymphocytes isolated from infected mammary glands of cows challenged with either Serratia marcescens or Staphylococcus uberis. Healthy Holstein cows in mid lactation were infected by intramammary infusion with S. marcescens or S. uberis. Following infection, milk samples were collected at various time points. Body temperatures of the cows were taken, and milk was analyzed for colony forming units (CFU) of bacteria and somatic cell counts (SCC). Leukocytes were isolated from the milk and analyzed by flow cytometry. Percentages and types of lymphocytes were determined as well as expression of CD62L, CD11a, LPAM-1 and CD44 on these cells. We found that the percentage of lymphocytes expressing either CD62L or CD11a showed a marked increase 12 h post infection (PI) with S. marcescens that was not seen in cows infected with S. uberis. Conversely, the percentage of lymphocytes expressing CD44 increased in cows infected with S. uberis at 12 h PI, but the increase was not seen in cows infected with S. marcescens. Expression of LPAM-1 was low at all time points in both groups of cows. Body temperatures became elevated in both groups of cows, peaking at 24 h PI in S. marcescens-infected cows and dropping thereafter. In contrast, temperatures of S. uberis-infected cows continued to rise and were still elevated 96 h PI. CFU of bacteria isolated from mammary glands of S. marcescens-infected cows dropped precipitously 24 h PI but continued at high levels in S. uberis-infected cows. SCC began falling in S. marcescens-infected cows 48 h PI but continued to increase in S. uberis-infected cows. Thus, a greater percentage of lymphocytes in milk had a phenotype consistent with recruitment from the peripheral pool following infection with S. marcescens than was seen following infection with S. uberis. Concurrent with the increases seen in percentages of this lymphocyte phenotype, clinical signs lessened in the S. marcescens-infected cows.