Differential recruitment of T- and IgA B-lymphocytes in the developing mammary gland in relation to homing receptors and vascular addressins

Maternal-Fetal Microchimerism: Impacts on Offspring's Immune Development and Transgenerational Immune Memory Transfer

Maternal-fetal microchimerism is a fascinating phenomenon in which maternal cells migrate to the tissues of the offspring during both pregnancy and breastfeeding. These cells primarily consist of leukocytes and stem cells. Remarkably, these maternal cells possess functional potential in the offspring and play a significant role in shaping their immune system development. T lymphocytes, a cell population mainly found in various tissues of the offspring, have been identified as the major cell type derived from maternal microchimerism. These T lymphocytes not only exert effector functions but also influence the development of the offspring's T lymphocytes in the thymus and the maturation of B lymphocytes in the lymph nodes. Furthermore, the migration of maternal leukocytes also facilitates the transfer of immune memory across generations. Maternal microchimerism has also been observed to address immunodeficiencies in the offspring. This review article focuses on investigating the impact of maternal cells transported within maternal microchimerism on the immune system development of the offspring, as well as elucidating the effector functions of maternal cells that migrate through the placenta and breast milk to reach the offspring.

Vedolizumab Does Not Affect Antibody Secreting Cell Recruitment to the Lactating Mammary Gland of Mothers With Inflammatory Bowel Disease

Despite a known role for α4β7 and MAdCAM-1 for the recruitment of antibody secreting cells to the lactating mammary gland, vedolizumab which targets integrin α4β7 did not lower breastmilk IgA in lactating mothers with IBD receiving the drug. It is likely that antibody secreting cells alternatively employ α4β1 to arrest on VCAM-1 also expressed by the lactating mammary gland.

The intestine: A highly dynamic microenvironment for IgA plasma cells

To achieve longevity, IgA plasma cells require a sophisticated anatomical microenvironment that provides cytokines, cell-cell contacts, and nutrients as well as metabolites. The intestinal epithelium harbors cells with distinct functions and represents an important defense line. Anti-microbial peptide-producing paneth cells, mucus-secreting goblet cells and antigen-transporting microfold (M) cells cooperate to build a protective barrier against pathogens. In addition, intestinal epithelial cells are instrumental in the transcytosis of IgA to the gut lumen, and support plasma cell survival by producing the cytokines APRIL and BAFF. Moreover, nutrients are sensed through specialized receptors such as the aryl hydrocarbon receptor (AhR) by both, intestinal epithelial cells and immune cells. However, the intestinal epithelium is highly dynamic with a high cellular turn-over rate and exposure to changing microbiota and nutritional factors. In this review, we discuss the spatial interplay of the intestinal epithelium with plasma cells and its potential contribution to IgA plasma cell generation, homing, and longevity. Moreover, we describe the impact of nutritional AhR ligands on intestinal epithelial cell-IgA plasma cell interaction. Finally, we introduce spatial transcriptomics as a new technology to address open questions in intestinal IgA plasma cell biology.

A cross-sectional study evidences regulations of leukocytes in the colostrum of mothers with obesity

BACKGROUND

Breastmilk is a dynamic fluid whose initial function is to provide the most adapted nutrition to the neonate. Additional attributes have been recently ascribed to breastmilk, with the evidence of a specific microbiota and the presence of various components of the immune system, such as cytokines and leukocytes. The composition of breastmilk varies through time, according to the health status of mother and child, and altogether contributes to the future health of the infant. Obesity is a rising condition worldwide that creates a state of systemic, chronic inflammation including leukocytosis. Here, we asked whether colostrum, the milk produced within the first 48 h post-partum, would contain a distinct leukocyte composition depending on the body mass index (BMI) of the mother.

METHODS

We collected peripheral blood and colostrum paired samples from obese (BMI > 30) and lean (BMI < 25) mothers within 48 h post-partum and applied a panel of 6 antibodies plus a viability marker to characterize 10 major leukocyte subpopulations using flow cytometry.

RESULTS

The size, internal complexity, and surface expression of CD45 and CD16 of multiple leukocyte subpopulations were selectively regulated between blood and colostrum irrespective of the study groups, suggesting a generalized cell-specific phenotype alteration. In obesity, the colostrum B lymphocyte compartment was significantly reduced, and CD16+ blood monocytes had an increased CD16 expression compared to the lean group.

CONCLUSIONS

This is the first characterization of major leukocyte subsets in colostrum of mothers suffering from obesity and the first report of colostrum leukocyte subpopulations in Latin America. We evidence various significant alterations of most leukocyte populations between blood and colostrum and demonstrate a decreased colostrum B lymphocyte fraction in obesity. This pioneering study is a stepping stone to further investigate active immunity in human breastmilk.

A Novel Pathway for Porcine Epidemic Diarrhea Virus Transmission from Sows to Neonatal Piglets Mediated by Colostrum

The mechanisms of colostrum-mediated virus transmission are difficult to elucidate because of the absence of experimental animal models and the difficulties in tissue sample collection from mothers in the peripartum period. Porcine epidemic diarrhea virus (PEDV) is a reemerging enteropathogenic coronavirus that has catastrophic impacts on the global pig industry. PEDV primarily infects neonatal piglets by multiple routes, especially 1- to 2-day-old neonatal piglets. Here, our epidemiological investigation and animal challenge experiments revealed that PEDV could be vertically transmitted from sows to neonatal piglets via colostrum, and CD3⁺ T cells in the colostrum play an important role in this process. The results showed that PEDV colonizing the intestinal epithelial cells (IECs) of orally immunized infected sows could be transferred to CD3⁺ T cells located just beneath the IECs. Next, PEDV-carrying CD3⁺ T cells, with the expression of integrin α4β7 and CCR10, migrate from the intestine to the mammary gland through blood circulation. Arriving in the mammary gland, PEDV-carrying CD3⁺ T cells could be transported across mammary epithelial cells (MECs) into the lumen (colostrum), as illustrated by an autotransfusion assay and an MECs/T coculture system. The PEDV-carrying CD3⁺ T cells in colostrum could be interspersed between IECs of neonatal piglets, causing intestinal infection via cell-to-cell contact. Our study demonstrates for the first time that colostrum-derived CD3⁺ T cells comprise a potential route for the vertical transmission of PEDV.

IMPORTANCE The colostrum represents an important infection route for many viruses. Here, we demonstrate the vertical transmission of porcine epidemic diarrhea virus (PEDV) from sows to neonatal piglets via colostrum. PEDV colonizing the intestinal epithelial cells could transfer the virus to CD3⁺ T cells located in the sow intestine. The PEDV-carrying CD3⁺ T cells in the sow intestine, with the expression of integrin α4β7 and CCR10, arrive at the mammary gland through blood circulation and are transported across mammary epithelial cells into the lumen, finally leading to intestinal infection via cell-to-cell contact in neonatal piglets. Our study not only demonstrates an alternative route of PEDV infection but also provides an animal model of vertical transmission of human infectious disease.

Broad Cross-Reactive IgA and IgG against Human Coronaviruses in Milk Induced by COVID-19 Vaccination and Infection

It is currently unclear if SARS-CoV-2 infection or mRNA vaccination can also induce IgG and IgA against common human coronaviruses (HCoVs) in lactating parents. Here we prospectively analyzed human milk (HM) and blood samples from lactating parents to measure the temporal patterns of anti-SARS-CoV-2 specific and anti-HCoV cross-reactive IgA and IgG responses. Two cohorts were analyzed: a vaccination cohort (n = 30) who received mRNA-based vaccines for COVID-19 (mRNA-1273 or BNT162b2), and an infection cohort (n = 45) with COVID-19 disease. Longitudinal HM and fingerstick blood samples were collected pre- and post-vaccination or, for infected subjects, at 5 time-points 14–28 days after confirmed diagnosis. The anti-spike(S) and anti-nucleocapsid(N) IgA and IgG antibody levels against SARS-CoV-2 and HCoVs were measured by multiplex immunoassay (mPlex-CoV). We found that vaccination significantly increased the anti-S IgA and IgG levels in HM. In contrast, while IgG levels increased after a second vaccine dose, blood and HM IgA started to decrease. Moreover, HM and blood anti-S IgG levels were significantly correlated, but anti-S IgA levels were not. SARS2 acute infection elicited anti-S IgG and IgA that showed much higher correlations between HM and blood compared to vaccination. Vaccination and infection were able to significantly increase the broadly cross-reactive IgG recognizing HCoVs in HM and blood than the IgA antibodies in HM and blood. In addition, the broader cross-reactivity of IgG in HM versus blood indicates that COVID-19 vaccination and infection might provide passive immunity through HM for the breastfed infants not only against SARS-CoV-2 but also against common cold coronaviruses.

Human Breast Milk: From Food to Active Immune Response With Disease Protection in Infants and Mothers

Breastfeeding is associated with long-term wellbeing including low risks of infectious diseases and non-communicable diseases such as asthma, cancer, autoimmune diseases and obesity during childhood. In recent years, important advances have been made in understanding the human breast milk (HBM) composition. Breast milk components such as, non-immune and immune cells and bioactive molecules, namely, cytokines/chemokines, lipids, hormones, and enzymes reportedly play many roles in breastfed newborns and in mothers, by diseases protection and shaping the immune system of the newborn. Bioactive components in HBM are also involved in tolerance and appropriate inflammatory response of breastfed infants if necessary. This review summarizes the current literature on the relationship between mother and her infant through breast milk with regard to disease protection. We will shed some light on the mechanisms underlying the roles of breast milk components in the maintenance of health of both child and mother.

Broad Cross-reactive IgA and IgG Against Human Coronaviruses in Milk Induced by COVID-19 Vaccination and Infection

It is currently unclear if SARS-CoV-2 infection or mRNA vaccination can also induce IgG and IgA against common human coronaviruses (HCoVs) in lactating parents. Here we prospectively analyzed human milk (HM) and blood samples from lactating parents to measure the temporal patterns of anti-SARS-CoV-2 specific and anti-HCoV cross-reactive IgA and IgG responses. Two cohorts were analyzed: a vaccination cohort (n=30) who received mRNA-based vaccines for COVID-19 (mRNA-1273 or BNT162b2), and an infection cohort (n=45) with COVID-19 disease. Longitudinal HM and fingerstick blood samples were collected pre- and post-vaccination or, for infected subjects, at 5 time-points 14 - 28 days after confirmed diagnosis. The anti-spike(S) and antinucleocapsid(N) IgA and IgG antibody levels against SARS-CoV-2 and HCoVs were measured by multiplex immunoassay (mPlex-CoV). We found that vaccination significantly increased the anti-S IgA and IgG levels in HM. In contrast, while IgG levels increased after a second vaccine dose, blood and HM IgA started to decrease. Moreover, HM and blood anti-S IgG levels were significantly correlated, but anti-S IgA levels were not. SARS2 acute infection elicited anti-S IgG and IgA that showed much higher correlations between HM and blood compared to vaccination. Vaccination and infection were able to significantly increase the broadly cross-reactive IgG recognizing HCoVs in HM and blood than the IgA antibodies in HM and blood. In addition, the broader cross-reactivity of IgG in HM versus blood indicates that COVID-19 vaccination and infection might provide passive immunity through HM for the breastfed infants not only against SARS-CoV-2 but also against common cold coronaviruses.

IMPORTANCE

It is unknown if COVID-19 mRNA vaccination and infection in lactating mothers results in cross-reactive antibodies against other common human coronaviruses. Our study demonstrates that mRNA vaccination and COVID-19 infection increase anti-spike SARS-CoV-2 IgA and IgG in both blood and milk. IgA and IgG antibody concentrations in milk were more tightly correlated with concentrations in blood after infection compared to mRNA vaccination. Notably, both infection and vaccination resulted in increased IgG against common seasonal β -coronaviruses. This suggests that SARS-CoV-2 vaccination or infection in a lactating parent may result in passive immunity against SARS-CoV-2 and seasonal coronaviruses for the recipient infant.

Influence of serum progesterone levels on the inflammatory response of female dogs with visceral leishmaniosis

The aim of this study was to evaluate the histopathological changes to the mammary gland that occur in female dogs with visceral leishmaniosis and to correlate the findings with the parasite load, inflammatory cell profile in mammary tissue and serum progesterone levels. For this, 20 adult female dogs that were naturally infected with Leishmania infantum, not spayed, not pregnant and free from mammary tumors were used. They were divided into two groups: G1 (n = 9) with high serum progesterone levels and G2 (n = 11) with low serum progesterone levels. The parasite load and the immunophenotype of leukocytes infiltrated into the mammary tissue (CD3, CD4, CD8 and MCA874) were evaluated using the immunohistochemical technique. In the mammary gland, chronic inflammatory infiltrate was mainly found in G1, sometimes associated with granulomatous inflammation, higher parasite load and higher density of cells immunolabeled for CD3, CD4, CD8 and MCA874. A significant positive correlation (p < 0.05) was observed between the parasite load and the immunolabeled leukocytes. The influence of the serum progesterone level in the mammary gland of infected female dogs can contribute to the maintenance of an immunosuppressive cell profile and favor the persistence of the parasite in this site.

The Gut‒Breast Axis: Programming Health for Life

The gut is a pivotal organ in health and disease. The events that take place in the gut during early life contribute to the programming, shaping and tuning of distant organs, having lifelong consequences. In this context, the maternal gut plays a quintessence in programming the mammary gland to face the nutritional, microbiological, immunological, and neuroendocrine requirements of the growing infant. Subsequently, human colostrum and milk provides the infant with an impressive array of nutrients and bioactive components, including microbes, immune cells, and stem cells. Therefore, the axis linking the maternal gut, the breast, and the infant gut seems crucial for a correct infant growth and development. The aim of this article is not to perform a systematic review of the human milk components but to provide an insight of their extremely complex interactions, which render human milk a unique functional food and explain why this biological fluid still truly remains as a scientific enigma.

Pre- and Probiotics to Increase the Immune Power of Colostrum in Dogs

Wide differences in Ig concentration in canine colostrum have been reported. Thus, some litters can be at risk of passive immune transfer failure. Present study evaluated if supplementation with MOS, FOS, E. faecium and L. acidophilus along pregnancy increases colostrum quality. Twenty Great Dane bitches were divided into 4 groups. Control group (CG) received standard diet, only. Diet was supplemented with pre- and probiotics in other 3 study groups during: the last (1WG), last 2 (2WG), and last 4 (4WG) weeks of pregnancy, until parturition. Serum samples were collected at estrous (T0), supplementation beginning (T1), and parturition (T2). Colostrum was collected at C-section end. The IgG, IgM, and IgA were assayed on both matrices. In serum, IgG were higher at T0 than at parturition in all study groups and they significantly lowered from T0 to T1 in all groups. In colostrum, IgG and IgM were significantly higher in 4WG, while IgA already increased in 2WG group. Four-week pre- and probiotic supplementation resulted in the best immune properties of colostrum, as by the higher IgG, IgM, and IgA colostrum levels found in 4WG. Further studies would verify the exact mechanisms involved: pre-partum IgG mammary accumulation and B-cells GALT proliferation and mammary transfer. Further trials would verify whether these beneficial effects of pre- and probiotics on colostrum also lead to improved clinical conditions and immunological functions of newborns and puppies.

Effects of oral administration of colostrum whey in peripartum goat on antimicrobial peptides in postpartum milk

The present study was conducted to examine whether colostrum supplementation in peripartum goats increases the antimicrobial peptides in their milk. Goats were orally administered 2 ml of colostrum whey products (colostrum group) or water (control group) daily, from 2 weeks before until 2 weeks after kidding. Body weights of mothers and kids were measured. Blood, milk, and fecal samples were collected from the mothers, and blood samples were collected from the kids. Concentrations of milk antimicrobial peptides (beta-defensin, cathelicidin, lactoferrin, S100A7, lactoperoxidase, and immunoglobulin A [IgA]) were determined. IgA and nutritional parameters (glucose, total cholesterol, triglyceride, ketone bodies, and non-esterified fatty acids) were also determined in the blood of mothers and kids. Milk IgA and lactoferrin concentrations were higher in the colostrum group than in the control group. Conversely, lower milk concentrations of S100A7 were observed in the colostrum group than that in the control group. Plasma IgA concentrations were higher for kids from the colostrum group than for those from the control group. These results suggest that oral administration of colostrum in pregnant goats increases IgA concentration in postpartum milk, which can subsequently improve the health of their kids.

Maternal Leukocytes and Infant Immune Programming during Breastfeeding

The fetal immune system develops in a rather sterile environment relative to the outside world and, therefore, lacks antigenic education. Soon after birth, the newborn is exposed to the hostile environment of pathogens. Recently, animal- and limited human-based studies have indicated that help from the mother, upon transfer of leukocytes and their products via breast milk feeding, greatly assists the newborn's immune system. Here, I discuss the newest advances on how milk leukocytes impact early life immunity, with an emphasis on the development of the infant T cell repertoire and early immune responses in the periphery and gut-associated lymphoid tissue. A deeper understanding of these novel mechanistic insights may inform potential translational approaches to improving immunity in infants.

Immunomodulatory effects of breast milk on food allergy

OBJECTIVE

To summarize the literature on immunomodulatory effects of breast milk on sensitization and possible mechanisms of action.

DATA SOURCES

Animal and human studies in PubMed that assessed breastfeeding or breast milk composition in food allergy.

STUDY SELECTIONS

All recent studies and some older key publications focusing on this topic.

RESULTS

Human milk composition is highly variable among mothers, which can affect the developing infant immune system. Human milk also affects the infant gut microbiome, which is associated with food allergy. High levels of human milk immune factors (IgA, cytokines, oligosaccharides) are associated with reduced risk of food allergy in the infant; it remains uncertain whether these are directly protective or biomarkers of transferred protection. Animal studies highlight potential mechanisms of protection provided by antigens, transforming growth factor β, and immunocomplexes, yet their relevance is poorly understood in humans. The role of food antigens in human milk in initial sensitization or tolerance induction is unclear.

CONCLUSION

The protection against allergy development provided by human milk may be attributable to the effect on the infant gut microbiome or direct effects on immune system. Studies evaluating the effect of breastfeeding and human milk composition on food allergy are needed.

Hormonal Regulation of Physiology, Innate Immunity and Antibody Response to H1N1 Influenza Virus Infection During Pregnancy

In 2009, the H1N1 swine flu pandemic highlighted the vulnerability of pregnant women to influenza viral infection. Pregnant women infected with influenza A virus were at increased risk of hospitalization and severe acute respiratory distress syndrome (ARDS), which is associated with high mortality, while their newborns had an increased risk of pre-term birth or low birth weight. Pregnant women have a unique immunological profile modulated by the sex hormones required to maintain pregnancy, namely progesterone and estrogens. The role of these hormones in coordinating maternal immunotolerance in uterine tissue and cellular subsets has been well researched; however, these hormones have wide-ranging effects outside the uterus in modulating the immune response to disease. In this review, we compile research findings in the clinic and in animal models that elaborate on the unique features of H1N1 influenza A viral pathogenesis during pregnancy, the crosstalk between innate immune signaling and hormonal regulation during pregnancy, and the role of pregnancy hormones in modulating cellular responses to influenza A viral infection at mid-gestation. We highlight the ways in which lung architecture and function is stressed by pregnancy, increasing baseline inflammation prior to infection. We demonstrate that infection disrupts progesterone production and upregulates inflammatory mediators, such as cyclooxygenase-2 (COX-2) and prostaglandins, resulting in pre-term labor and spontaneous abortions. Lastly, we profile the ways in which pregnancy alters innate and adaptive cellular immune responses to H1N1 influenza viral infection, and the ways in which these protect fetal development at the expense of effective long-term immune memory. Thus, we highlight advancements in the field of reproductive immunology in response to viral infection and illustrate how that knowledge might be used to develop more effective post-infection therapies and vaccination strategies.

Immunologically Active Components in Human Milk and Development of Atopic Disease, With Emphasis on Food Allergy, in the Pediatric Population

Breast-feeding is currently recommended to prevent the development of allergic diseases; however, data are conflicting and mechanisms are unclear. The immunomodulatory composition of human milk is poorly characterized and varies between mothers. We and others have shown that high levels of human milk IgA and certain cytokines and human milk oligosaccharides are associated with protection against food allergy in the infant, but it is unclear whether they are responsible for or simply biomarkers of the vertical transfer of protection. Because human milk has pre- and probiotic properties, the anti-allergy protection afforded by human milk may be due to its control on the developing gut microbiome. In mice, murine milk IgA supports gut homeostasis and shapes the microbiota, which in turn diversifies the intestinal IgA repertoire that reciprocally promotes the diversity of gut microbiome; these mechanisms are poorly understood in humans. In addition, several human milk bioactives are immunostimulatory, which may in part provide protection against allergic diseases. The regulation of immunologically active components in human milk is incompletely understood, although accumulating evidence suggests that IgA and cytokines in human milk reflect maternal exposures. This review summarizes the current literature on human milk components that have been associated with protection against food allergy and related allergic disorders in early childhood and discusses the work relating to regulation of these levels in human milk and possible mechanisms of action.

Breast milk IgA to foods has different epitope specificity than serum IgA-Evidence for entero-mammary link for food-specific IgA?

BACKGROUND

We have previously shown that maternal cow's milk (CM) elimination results in downregulation of CM-specific IgA antibody levels in BM, but not in serum, suggesting that an entero-mammary link may exist for food-specific antibody-secreting cells.

OBJECTIVE

We sought to investigate whether food-specific IgA epitope profiles differ intra-individually between mother's serum and BM. We also examined how infants' food epitope-specific IgA develops in early infancy and the relationship of IgA epitope recognition with development of cow's milk allergy (CMA).

METHODS

We measured specific IgA to a series of overlapping peptides in major CM allergens (α_s1 -, α_s2 -, β- and κ-caseins and β-lactoglobulin) in paired maternal and infant serum as well as BM samples in 31 mother-infant dyads within the first 15 post-partum months utilizing peptide microarray.

RESULTS

There was significant discordance in epitope specificity between BM and maternal sera ranging from only 13% of sample pairs sharing at least one epitope in α_s1 -casein to 73% in κ-casein. Epitope-specific IgA was detectable in infants' sera starting at less than 3 months of age. Sera of mothers with a CMA infant had increased binding of epitope-specific IgA to CM proteins compared to those with a non-CMA infant.

CONCLUSION & CLINICAL RELEVANCE

These findings support the concept that mother's milk has a distinct antifood antibody repertoire when compared to the antibody repertoire of the peripheral blood. Increased binding of serum epitope-specific IgA to CM in mothers of infants with CMA may reflect inherited systemic immunogenicity of CM proteins in these families, although specific IgA in breast milk was not proportionally up-regulated.

Role of Prolactin in Promotion of Immune Cell Migration into the Mammary Gland

Immune cells in the mammary gland play a number of important roles, including protection against infection during lactation and, after passing into milk, modulation of offspring immunity. However, little is known about the mechanism of recruitment of immune cells to the lactating gland in the absence of infection. Given the importance of prolactin to other aspects of lactation, we hypothesized it would also play a role in immune cell recruitment. Prolactin treatment of adult female mice for a period equivalent to pregnancy and the first week of lactation increased immune cell flux through the mammary gland, as reflected in the number of immune cells in mammary gland-draining, but not other lymph nodes. Conditioned medium from luminal mammary epithelial HC11 cell cultures was chemo-attractive to CD4+ and CD8+ T cells, CD4+ and CD8+ memory T cells, B cells, macrophages, monocytes, eosinophils, and neutrophils. Prolactin did not act as a direct chemo-attractant, but through effects on luminal mammary epithelial cells, increased the chemo-attractant properties of conditioned medium. Macrophages and neutrophils constitute the largest proportion of cells in milk from healthy glands. Depletion of CCL2 and CXCL1 from conditioned medium reduced chemo-attraction of monocytes and neutrophils, and prolactin increased expression of these two chemokines in mammary epithelial cells. We conclude that prolactin is an important player in the recruitment of immune cells to the mammary gland both through its activities to increase epithelial cell number as well as production of chemo-attractants on a per cell basis.

Lactogenic immunity and vaccines for porcine epidemic diarrhea virus (PEDV): Historical and current concepts

Morbidity, mortality, and loss of productivity from enteric diseases in neonatal piglets cost swine producers millions of dollars annually. In 2013-2014, the porcine epidemic diarrhea virus (PEDV) outbreak led to $900 million to $1.8 billion in annual losses to US swine producers. Passive lactogenic immunity remains the most promising and effective way to protect neonatal suckling piglets from enteric diseases like PEDV. Protecting suckling piglets through lactogenic immunity is dependent on trafficking of pathogen-specific IgA plasmablasts to the mammary gland and accumulation of secretory IgA (sIgA) antibodies in milk, defined as the gut-mammary-sIgA axis. Due to an impermeable placenta, piglets are born agammaglobulinic, and are highly susceptible to a plethora of infectious agents. They rely solely on colostrum and milk antibodies for maternal lactogenic immunity. Previous advances in the development of live and attenuated vaccines for another devastating diarrheal virus of pigs, transmissible gastroenteritis virus (TGEV), provide insights into the mechanisms of maternal immunity and piglet protection. In this chapter, we will review previous research on TGEV-induced lactogenic immunity to provide a historical perspective on current efforts for PEDV control and vaccines in the swine industry. Identifying factors that influence lactogenic immunity and the gut-mammary-sIgA axis may lead to improved vaccine regimens for PEDV and other enteric pathogens in gestating swine and improved overall herd immunity, swine health and industry productivity.

Transfer of Maternal Immune Cells by Breastfeeding: Maternal Cytotoxic T Lymphocytes Present in Breast Milk Localize in the Peyer's Patches of the Nursed Infant

Despite our knowledge of the protective role of antibodies passed to infants through breast milk, our understanding of immunity transfer via maternal leukocytes is still limited. To emulate the immunological interface between the mother and her infant while breast-feeding, we used murine pups fostered after birth onto MHC-matched and MHC-mismatched dams. Overall, data revealed that: 1) Survival of breast milk leukocytes in suckling infants is possible, but not significant after the foster-nursing ceases; 2) Most breast milk lymphocytes establish themselves in specific areas of the intestine termed Peyer’s patches (PPs); 3) While most leukocytes in the milk bolus were myeloid cells, the majority of breast milk leukocytes localized to PPs were T lymphocytes, and cytotoxic T cells (CTLs) in particular; 4) These CTLs exhibit high levels of the gut-homing molecules α4β7 and CCR9, but a reduced expression of the systemic homing marker CD62L; 5) Under the same activation conditions, transferred CD8 T cells through breast milk have a superior capacity to produce potent cytolytic and inflammatory mediators when compared to those generated by the breastfed infant. It is therefore possible that maternal CTLs found in breast milk are directed to the PPs to compensate for the immature adaptive immune system of the infant in order to protect it against constant oral infectious risks during the postnatal phase.

The Mammary Gland in Mucosal and Regional Immunity

The mammary gland (MG) lacks a mucosa but is part of the mucosal immune system because of its role in passive mucosal immunity. The MG is not an inductive site for mucosal immunity. Rather, synthesis of immunoglobulin (Ig)A by plasma cells stimulated at distal inductive sites dominate in the milk of rodents, humans, and swine whereas IgG1 derived from serum predominates in ruminants. Despite the considerable biodiversity in the role of the MG, IgG passively transfers the maternal systemic immunological experience whereas IgA transfers the mucosal immunological experience. Although passive antibodies are protective, they and other lacteal constituents can be immunoregulatory. Immune protection of the MG largely depends on the innate immune system; the monocytes–macrophages group together with intraepithelial lymphocytes is dominant in the healthy gland. An increase in somatic cells (neutrophils) and various interleukins signal infection (mastitis) and a local immune response in the MG. The major role of the MG to mucosal immunity is the passive immunity supplied to the suckling neonate.

1-Kestose consumption during pregnancy and lactation increases the levels of IgA in the milk of lactating mice

To examine the effect of dietary supplementation with 1-kestose on the IgA levels in milk, BALB/c mice were fed diets with or without 5% 1-kestose during pregnancy and lactation. The total and specific IgA levels in the milk were measured at 7 and 14 days after delivery. A two-way ANOVA with repeated measures resulted in a significant effect of 1-kestose-supplementation on total IgA concentrations (p < 0.05) and the level of anti-Bacteroides IgA (p < 0.05). A significant positive correlation was found between the mean count of Bacteroides spp. in maternal feces and the total IgA concentration in maternal milk (r = 0.55, p < 0.05), suggesting a potential link between the gut and mammary gland immune system. In conclusion, this study demonstrated the effects of dietary prebiotics on milk IgA production.

Influence of terminal differentiation and PACAP on the cytokine, chemokine, and growth factor secretion of mammary epithelial cells

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide with trophic and cytoprotective effects, has been shown to affect cell survival, proliferation, and also differentiation of various cell types. The high PACAP level in the milk and its changes during lactation suggest a possible effect of PACAP on the differentiation of mammary epithelial cells. Mammary cell differentiation is regulated by hormones, growth factors, cytokines/chemokines, and angiogenic proteins. In this study, differentiation was hormonally induced by lactogenic hormones in confluent cultures of HC11 mouse mammary epithelial cells. We investigated the effect of PACAP on mammary cell differentiation as well as release of cytokines, chemokines, and growth factors. Differentiation was assessed by expression analysis of the milk protein β-casein. Differentiation significantly decreased the secretion of interferon gammainduced protein (IP)-10, "regulated upon activation normal T cell expressed and presumably secreted" (RANTES), insulin-like growth factor-binding protein (IGFBP)-3 and the epidermal growth factor receptor (EGFR) ligands, such as epidermal growth factor (EGF) and amphiregulin (AREG). The changes in the levels of IP-10 and RANTES may be relevant for the alterations in homing of T cells and B cells at different stages of mammary gland development, while the changes of the EGFR ligands may facilitate the switch from proliferative to lactating stage. PACAP did not modulate the expression of β-casein or the activity of hormone-induced pathways as determined by the analysis of phosphorylation of Akt, STAT5, and p38 MAPK. However, PACAP decreased the release of EGF and AREG from non-differentiated cells. This may influence the extracellular signal-related transactivation of EGFR in the non-differentiated mammary epithelium and is considered to have an impact on the modulation of oncogenic EGFR signaling in breast cancer.

Impaired mammary gland T cell population during early lactation in hypoprolactinemic lactation-deficient rats

Mammary stroma is composed of various cell types, including migratory leukocytes. Although mammary antibody-secreting cells have been extensively studied, reports focusing on mammary T cells are scarce. It is thought that the recruitment mechanism of leukocytes to the mammary gland (MG) is controlled by pregnancy- and lactation-specific stimuli. But whether prolactin (PRL) modulates the T-cell population in MG is still unknown. Our aim was to study the relationship between PRL levels and T and B cells during early lactation (L2, day 2 post partum) and mid-lactation (L12, day 12 of lactation). In order to investigate whether PRL is associated with homing events to MG, female Sprague Dawley (SD) and SD-derived desmoglein 4−/− hairless (phenotype with lactation deficit, OFA hr/hr) rats were killed during estrus, pregnancy, and post partum, and blood, MG, and corpora lutea were obtained to perform fluorescent-activated cell sorting (FACS), real-time PCR, and histological and RIA studies. Serum PRL levels were lower in OFA hr/hr rats than in SD rats during early lactation. MG of OFA hr/hr rats showed less secretory material compared with SD rats. FACS analysis showed lower percentage of MG CD3+ cells in OFA hr/hr rats compared with SD rats on L2 and L12. OFA hr/hr rats showed higher absolute numbers of circulating CD3+ cells compared with SD rats on L2 but not on L12. These results show that T-cell population in MG is affected in early lactating OFA hr/hr rats and strongly suggest that serum PRL levels may be involved in the homing events to MG, probably helping antibody-secreting cells and protecting the gland during lactation development.

Supplemental β-carotene increases IgA-secreting cells in mammary gland and IgA transfer from milk to neonatal mice

Mortality of neonates continues to be a major problem in humans and animals. IgA provides protection against microbial antigens at mucosal surfaces. Although β-carotene supplementation has been expected to enhance retinoic acid-mediated immune response in neonates, the exact mechanism by which β-carotene enhances IgA production is still unclear. We investigated the effect of supplemental β-carotene for maternal mice during pregnancy and lactation on IgA antibody-secreting cells (ASC) in mammary gland and guts and on IgA transfer from milk to neonatal mice. Pregnant mice were fed untreated or 50 mg/kg β-carotene-supplemented diets from 6·5 d postcoitus (dpc) to 14 d postpartum (dpp). Supplemental β-carotene increased the numbers of IgA ASC in mammary gland (P < 0·05) and ileum (P < 0·001), and also mRNA expression of IgA C-region in ileum (P < 0·05) of maternal mice at 14 dpp, but few IgA ASC were detected in mammary gland at 17·5 dpc. IgA concentration in stomach contents, which represents milk IgA level, was significantly higher (P < 0·01) in neonatal mice born to β-carotene-supplemented mothers at 7 and 14 dpp, and IgA concentration in serum, stomach contents and faeces increased (P < 0·001) drastically with age. These results suggest that β-carotene supplementation for maternal mice during pregnancy and lactation is useful for enhancing IgA transfer from maternal milk to neonates owing to the increase in IgA ASC in mammary gland and ileum during lactation.

IgA ASC accumulation to the lactating mammary gland is dependent on VCAM-1 and alpha4 integrins

The homing and migration of IgA antibody secreting cells (ASC) to the lactating mammary gland is essential to the passive transfer of immunity from mother to nursing neonate. Antibody secreting cells, located within the lactating mammary gland, produce high levels of antigen-specific IgA antibodies. These antibodies, which are subsequently transferred to the nursing neonate via breast milk, provide passive immune protection against antigens previously encountered by the mother to the nursing infant. The efficient homing and accumulation of lymphocytes is highly dependent on cellular adhesion molecules expressed on the vascular endothelium and their integrin ligands. Vasculature within the lactating mammary gland is known to express several adhesion molecules, including VCAM-1 and MAdCAM-1. However, the role of these molecules in vivo has not been previously described. Here we show that alpha4 integrins and VCAM-1 play essential roles in mediating the accumulation of IgA ASCs to the lactating mammary gland. Conversely, neither MAdCAM-1 nor its major ligand alpha4beta7 are required for efficient IgA ASC accumulation to this tissue.

Antibody-mediated protection against infection with Helicobacter pylori in a suckling mouse model of passive immunity

Studies of active immunization against Helicobacter pylori indicate that antibodies play a minor role in immunity. There is also evidence, however, that the translocation of antibodies in the stomach may be insufficient to achieve functional antibody levels in the gastric lumen. We have used a suckling mouse model of passive immunity to determine if perorally delivered antibodies can protect against infection with H. pylori. Female C57BL/6 mice were immunized parenterally with formalin-fixed cells of three clinical isolates of H. pylori (3HP) or the mouse-adapted H. pylori strain SS1 before mating. Their pups were challenged with the SS1 strain at 4 days of age and left to suckle before determination of bacterial loads 14 days later. Compared to age-matched controls, pups suckled by 3HP-vaccinated dams were significantly protected against infection (>95% reduction in median bacterial load; P<0.0001). Pups suckled by SS1-vaccinated dams were also significantly protected in terms of both median bacterial load (>99.5% reduction; P<0.0001) and the number of culture-negative pups (28% versus 2% for immune and nonimmune cohorts, respectively; P<0.0001). Similar results were obtained with pups suckled by dams immunized with a urease-deficient mutant of SS1. Fostering experiments demonstrated that protection was entirely attributable to suckling from an immunized dam, and antibody isotype analysis suggested that protection was mediated by the immunoglobulin G fraction of immune milk. Analysis of the bacterial loads in pups sampled before and after weaning confirmed that infection had been prevented in culture-negative animals. These data indicate that antibodies can prevent colonization by H. pylori and suppress the bacterial loads in animals that are colonized.

Effects on adhesion molecule expression and lymphocytes in the bovine mammary gland following intra-mammary immunisation

Changes to adhesion molecule expression and lymphocyte populations were evaluated in alveolar mammary tissue collected from cows following an immunisation protocol that involved intra-mammary inoculation to induce an IgA response in mammary secretions. The right quarters of the udder were immunised; the left side acted as a control. Antibody titres in secretions showed that at least two animals responded with antigen-specific IgA. Numbers of T-lymphocytes were 4-fold higher in immunised glands compared with controls (P<0.05). IgA-, IgM- and IgG-positive cell numbers were significantly higher (P<0.01) in immunised glands compared with controls in three of the four cows. No mucosal addressin molecule-1 (MAdCAM-1), vascular cell-adhesion molecule-1 (VCAM-1) or peripheral node addressin (PNAd) protein expression was detected on smaller venules that stained positively for von Willebrand factor in alveolar mammary tissues, from either immunised or control glands. Both VCAM-1 and PNAd were detected on smaller venules in supramammary lymph nodes, however, there was no significant difference between immunised and control glands. Quantification of MAdCAM-1 mRNA showed very low expression in both immunised and control alveolar tissue compared with Peyer's patch positive-control tissue. These findings suggest that the bovine mammary gland is capable of a mucosal antibody response; however, MAdCAM-1 is not involved with lymphocyte homing to the mammary gland in this species.

Humoral and cellular factors of maternal immunity in swine

Immunoglobulins cannot cross the placenta in pregnant sows. Neonatal pigs are therefore agammaglobulinemic at birth and, although immunocompetent, they cannot mount rapid immune responses at systemic and mucosal sites. Their survival depends directly on the acquisition of maternal immunity via colostrum and milk. Protection by maternal immunity is mediated by a number of factors, including specific systemic humoral immunity, involving mostly maternal IgG transferred from blood to colostrum and typically absorbed within the first 36 h of life. Passive mucosal immunity involves local humoral immunity, including the production of secretory IgA (sIgA), which is transferred principally via milk until weaning. The mammary gland (MG) produces sIgA, which is, then secreted into the milk via the poly-Ig receptor (pIgR) of epithelial cells. These antibodies are produced in response to intestinal and respiratory antigens, including pathogens and commensal organisms. Protection is also mediated by cellular immunity, which is transferred via maternal cells present in mammary secretions. The mechanisms underlying the various immunological links between MG and the mucosal surfaces involve hormonally regulated addressins and chemokines specific to these compartments. The enhancement of colostrogenic immunity depends on the stimulation of systemic immunity, whereas the enhancement of lactogenic immunity depends on appropriate stimulation at induction sites, an increase in cell trafficking from the gut and upper respiratory tract to the MG and, possibly, enhanced immunoglobulin production at the effector site and secretion in milk. In addition, mammary secretions provide factors other than immunoglobulins that protect the neonate and regulate the development of mucosal immunity--a key element of postnatal adaptation to environmental antigens.

Identification in milk of a serum amyloid A peptide chemoattractant for B lymphoblasts

Background

Normal mammary gland contains an extravascular population of B lymphoblasts, precursors of the immunoglobulin plasma cells that play a key role in the passive protection of neonates by secreting immunoglobulins to colostrum and milk. We investigated the presence of chemoattractants in the milk by analysing the chemoattractant activity of various fractions of this secretion. Milk chemoattractants are potentially involved in the recruitment of lymphocytes from the maternal bloodstream in lactating mammary glands.

Results

The dilution-related lymphoid cell chemoattraction of whey was associated with a < 10 kDa ultrafiltrate. Active fractions were purified by reverse-phase high performance liquid chromatography. Two peptides of 2.7 kDa (DMREANYKNSDKYFHARGNYDAA) and 1 kDa (RPPGLPDKY) were identified as fragments of the SAA protein family, tentatively identified as SAA2. Only the 2.7 kDa synthetic peptide displayed chemotactic activity, at two different optimal concentrations. At the lower concentration (3.7 nM), it attracted B-cell lymphoblasts, whereas at the higher (3.7 μM), it attracted B lymphocytes. Then, the SAA mRNA expression was analysed and we observed more SAA transcripts during lactation than gestation.

Conclusion

These data are consistent with the SAA_23–45 fragment being involved in preplasma B-cell recruitment to the mammary gland and resultant benefit to the neonate.

An indispensable role for the chemokine receptor CCR10 in IgA antibody-secreting cell accumulation

The differential expression of chemokines and chemokine receptors, by tissues and leukocytes, respectively, contributes to the specific accumulation of leukocyte subsets to different tissues. CCR10/CCL28 interactions are thought to contribute to the accumulation of IgA Ab-secreting cells (ASC) to mucosal surfaces, such as the gastrointestinal tract and the lactating mammary gland. Although the role of CCL28 in lymphocyte homing is well established, direct in vivo evidence for CCR10 involvement in this process has not been previously shown. In this study, we describe the generation of a CCR10-deficient mouse model. Using this model, we demonstrate that CCR10 is critical for efficient localization and accumulation of IgA ASC to the lactating mammary gland. Surprisingly, IgA ASC accumulation to the gastrointestinal tract is minimally impacted in CCR10-deficient mice. These results provide the first direct evidence of CCR10 involvement in lymphocyte homing and accumulation in vivo, and demonstrate that reliance on CCR10-mediated recruitment of IgA ASC varies dramatically within mucosal tissues.

Membrane markers of the immune cells in swine: an update

Besides their breeding value, swine are increasingly used as biomedical models. As reported in three international swine clusters of differentiation (CD) workshops and in the animal homologue section of the last workshop for the determination of human leukocyte differentiation antigens (HLDA 8), characterisation of leukocyte surface antigens by monoclonal antibodies and other molecular studies have determined the cell lineages and blood leukocyte subsets implicated in the immune response, including cell adhesion molecules involved in cell trafficking. This review focusses on the current state of knowledge of porcine leukocyte differentiation and major histocompatibility complex (SLA) molecules. Examples of porcine particularities such as the double-positive T lymphocytes with the phenotype CD(4+)CD8(low) and CD(4-)CD8(low) alphabeta T cell subsets and the persistence of SLA class II after T-lymphocyte activation are illustrated, as well as the shared characteristics of the Artiodactyla group, such as the high proportion of gammadelta TcR (T cell receptor) T cells in blood and other lymphoid tissues. Furthermore, discrepancies between swine and humans, such as CD16 expression on dendritic cells and CD11b (wCD11R1) tissue distribution are outlined. The rapidly growing information should facilitate manipulation of the swine immune system towards improving disease control, and open new avenues for biomedical research using the pig as a model.

A biological context for the self-nonself discrimination and the regulation of effector class by the immune system

An effective immune response to an antigen requires two sets of decisions: Decision 1, the sorting of the repertoire, and Decision 2, the regulation of effector class. The repertoire, because it is somatically generated, large, and random, must be sorted by a somatic mechanism that subtracts those specificities (anti-self) that, if expressed, would debilitate the host, leaving a residue (anti-nonself) that, if not expressed, would result in the death of the host by infection. The self-nonself discrimination is the metaphor used to describe Decision 1, the sorting of the repertoire. In order to be functional, the sorted repertoire must be coupled to a set of biodestructive and ridding effector functions, such that the response to each antigen is treated in a coherent and independent manner. Although a reasonably complete framework for Decision 1 exists, Decision 2 lacks conceptualization. The questions that must be considered to arrive at a proper framework are posed. It should be emphasized that manipulation at the level of Decision 2 is where clinical applications are likely to be found.

Molecular cloning and functional characterization of porcine CCL28: Possible involvement in homing of IgA antibody secreting cells into the mammary gland

Constitutive expression of chemokines by epithelial cells controls the recruitment and the localization of specialized lymphocytes. Mucosae associated-epithelial chemokine (MEC/CCL28) cloned from porcine salivary gland and colon tissues consisted of an open reading frame (ORF) of 384-bp coding for 127 amino-acids protein with 22 residues signal sequence. The resulting mature protein is composed of 105 aa with 4 conserved cysteine residues. CCL28 shows aa sequence identity with rat, mouse, macaque and human ranging from 67 to 87%. Using plasmid pQETris-CCL28 injection, a rabbit anti-serum was produced and showed a specific reactivity towards non-reduced form of CCL28 recombinant protein. Comparatively to CCL25 mRNA expression, RT-PCR analysis showed that CCL28 is expressed in various mucosal tissues, but most abundantly in nasal mucosa, colon, salivary and mammary gland (MG). Immunohistochemical analysis showed that CCL28 is produced by epithelial cells of these tissues suggesting that this chemokine can play an important role by linking homing mechanisms between the gut, nasal mucosa and MG. In addition, mRNA of CCL28 was up-regulated in the MG at late gestation and during lactation but was not found at weaning. CCL28 protein was excreted in sow's milk sustaining that this chemokine plays a key role of IgA-ASCs accumulation in this tissue and thus controls the passive transfer level of IgA antibodies from mother to infant.

Immune components of colostrum and milk--a historical perspective

Key developments in the understanding of the immune functions of milk and colostrum are reviewed, focusing on their proteinaceous components. The topics covered include the immunoglobulins, immune cells, immunomodulatory substances, and antimicrobial proteins. The contributions of new technologies and the introduction of fresh approaches from other fields are highlighted, as are the contributions that mammary biology research has made to the development of other fields. Finally, a summary of some current outstanding questions and likely future directions of the field are given.

Maternal breast-milk and intestinal bifidobacteria guide the compositional development of the Bifidobacterium microbiota in infants at risk of allergic disease

BACKGROUND

The sources and the impact of maternal bacteria on the initial inoculum of the intestinal microflora of newborn infants remain elusive.

OBJECTIVE

To assess the association between maternal breast-milk and fecal bifidobacteria and infants' fecal bifidobacteria.

METHODS

Sixty-one mother-infant pairs were included, special emphasis being placed on the maternal allergic status. Bifidobacteria were analysed by a direct PCR method in fecal samples from mothers at 30-35 weeks of gestation and from infants at 1 month of age and from breast-milk samples 1 month post-partum.

RESULTS

Fecal Bifidobacterium adolescentis and Bifidobacterium bifidum colonization frequencies and counts among mother-infant pairs correlated significantly (P=0.005 and 0.02 for frequencies, respectively, and P=0.002 and 0.01 for counts, respectively). Only infants of allergic, atopic mothers were colonized with B. adolescentis. Each of the breast-milk samples contained bifidobacteria [median 1.4 x 10(3) bacterial cells/mL; interquartile range (IQR) 48.7-3.8 x 10(3)]. Bifidobacterium longum was the most frequently detected species in breast-milk. Allergic mothers had significantly lower amounts of bifidobacteria in breast-milk compared with non-allergic mothers [median 1.3 x 10(3) bacterial cells/mL (IQR 22.4-3.0 x 10(3)) vs. 5.6 x 10(3) bacterial cells/mL (1.8 x 10(3)-1.8 x 10(4)), respectively, (P=0.004)], and their infants had concurrently lower counts of bifidobacteria in feces [3.9 x 10(8) bacterial cells/g (IQR 6.5 x 10(6)-1.5 x 10(9)) in infants of allergic mothers, vs. 2.5 x 10(9) bacterial cells/g (6.5 x 10(8)-3.2 x 10(10)) in infants of non-allergic mothers, P=0.013].

CONCLUSIONS

Breast-milk contains significant numbers of bifidobacteria and the maternal allergic status further deranges the counts of bifidobacteria in breast-milk. Maternal fecal and breast-milk bifidobacterial counts impacted on the infants' fecal Bifidobacterium levels. Breast-milk bacteria should thus be considered an important source of bacteria in the establishment of infantile intestinal microbiota.

Traffic of endogenous, transduced, and endocytosed prolactin in rabbit lacrimal acinar cells

The rabbit lacrimal gland undergoes an immunophysiological transformation during pregnancy, reminiscent of that of the mammary gland as it prepares to deliver secretory IgA into the nascent fluid product. The contents of TGF-beta and prolactin (PRL) within ductal epithelial cells increase, and their primary localizations shift from the apical to the basal cytoplasm, suggesting a transformation from exocrine to paracrine secretion. Studies with ex vivo acinar cell models demonstrated that elevated PRL suppresses traffic of secretory proteins into the regulated exocrine apparatus and directs them into a novel, induced, regulated paracrine apparatus [Wang, Y., Chiu, C.T., Nakamura, T., Walker, A.M., Petridou, B., Trousdale M.D., Hamm-Alvarez S.F., Schechter J.E., Mircheff A.K., 2007. Elevated prolactin redirects secretory vesicle traffic in rabbit lacrimal acinar cells. Am. J. Physiol. Endocrinol. Metab. 292, E1122-E1134]. However, it was not clear whether PRL itself entered the induced paracrine apparatus. In the present study, confocal immunofluorescence microscopy revealed that natively expressed PRL and over-expressed PRL co-localized with PRL receptors (PRLR); rab11, a marker for the recycling endosome; gamma-adaptin, a marker for the Golgi complex and trans-Golgi network; and rab7, a marker for the autophagic lysosomal apparatus. Natively expressed, over-expressed, and endocytosed PRL also co-localized with rab4 and rab5A, markers for the early endosome, and with rab3D, a marker for regulated exocrine secretory vesicles. Endocytosed PRL was stored in intact form and released in response to stimulation with carbachol. Subcellular fractionation analysis detected relative excesses of PRL over PRLR in fractions that contained fragments of the recycling endosome and fractions that contained both secretory vesicle fragments and prelysosomal and autolysosomal fragments. EM-gold microscopy demonstrated PRL within small vesicles, consistent with endosomes or secondary lysosomes, and in large vesicles, consistent with regulated secretory vesicles. The secretory vesicles were preponderantly localized in the apical cytoplasm of control cells, and in the basal cytoplasm of PRL over-expressing cells. These results indicate that when lacrimal epithelial cells synthesize PRL, and when they endocytose it from their ambient medium, they traffic it both into the endosomes that constitute the constitutive transcytotic paracrine apparatus and also into regulated secretory vesicles, which are associated with the exocrine apparatus at low PRL levels and with the induced paracrine apparatus at high PRL levels.

Effects of dietary scFOS on immunoglobulins in colostrums and milk of bitches

Fructo-oligosaccharides (scFOS) are prebiotic ingredients that improve protection against pathogens probably through promoting the growth of gastrointestinal bacteria-like Bifidobacteria and Lactobacilli: this stimulation may lead to a better development of immune repertoire and/or stimulation of the local immune response. According to the existence of the immune entero-mammary link, we were wondering if the dietary supplementation with scFOS could enhance the mucosal immunoglobulin level in mammary secretions. Results in this study show that bitches supplemented with scFOS exhibit higher colostrum and milk IgM content without concomitant effect on IgG1, IgG2 and IgA. In addition, intranasally immunized puppies exhibited a trend to higher Bordetella bronchiseptica-specific IgM immune response. The dietary supplementation with scFOS increased the IgM level in colostrums and milk of bitches by mechanisms which remain to be elucidated.

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.

Expression of TECK/CCL25 and MEC/CCL28 chemokines and their respective receptors CCR9 and CCR10 in porcine mucosal tissues

CCL25 and CCL28 (also named TECK and MEC) are CC chemokines primarily expressed by thymic dendritic cells and mucosal epithelial cells. The cognate receptors of CCL25 and CCL28, named CCR9 and CCR10, are mainly expressed on T lymphocytes for CCR9 and IgA(+) and IgM(+) plasmablasts for CCR9 and CCR10, respectively. In human and mouse, chemokines CCL25 and CCL28 play an important role in attracting immune cells to the gastrointestinal tract and in controlling segmental specialization of the intestinal immune system. To investigate if CCL25 and CCL28 play a similar role in the pig and to better understand lymphocyte trafficking in this species, we cloned porcine CCL25 and CCR10 and measured expression of CCL25, CCL28, CCR9, and CCR10 transcripts by real-time and conventional PCR in various tissues from newborn and young piglets, and adult sows. The results of the expression analyses show that (i) expression of CCL25 mRNA is mainly restricted to the small intestine, (ii) CCL28 mRNA expression is detectable in all tested epithelial mucosal surfaces with the highest levels of expression in the mammary gland, trachea and large intestine, (iii) high levels of expression of CCR9 mRNA in CD3+ T lymphocytes, gut-associated lymphoid tissues (GALT), and the small intestine, (iv) high levels of expression of CCR10 mRNA in GALT, the large intestine, the small intestine, and the mammary gland, and (v) up-regulation of CCL28 mRNA expression during lactation in the mammary gland. This pattern of expression, which is discussed in the context of compartmentalization of the porcine common mucosal immune system into upper aero-digestive tract, small intestine and large intestine, suggests a key role for CCL28 in the recruitment of IgA secreting cells into the mammary gland enabling the passive transfer of IgA antibodies from mother to infant.

MAdCAM-1 expression and regulation in murine colonic endothelial cells in vitro

BACKGROUND

Although the mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is associated with the etiology of inflammatory bowel diseases, few studies have directly examined MAdCAM-1 using microvascular endothelium derived from the colon. This study measured the expression of MAdCAM-1 in a novel colon endothelial line MJC-1, as well as MAdCAM-1 regulation and function in vitro.

METHODS

We cloned microvascular endothelial cells from primary colon cultures using ImmortoMice mice (whose cells express a temperature-sensitive SV40 large T antigen, H-2Kb-tsA58 mice). Expression of MAdCAM-1 after stimulation with cytokines [tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, or interferon (IFN)-gamma] was determined by Western blotting. Signal paths regulating MAdCAM-1 expression were examined using pharmacological blockers before cytokines. We also examined lymphocyte adhesion using lymphocytes that constitutively express alpha4beta7 integrin.

RESULTS

TNF-alpha induced MAdCAM-1 in a dose-dependent manner by 24 hours. MAdCAM-1 induction was protein kinase C, tyrosine kinase, p38 mitogen activated protein kinase, and nuclear-factor kappa-B/poly adenosine diphosphate ribose polymerase dependent. Lymphocyte adhesion was increased 2.6-fold after TNF-alpha stimulation and was inhibited by anti-MAdCAM-1 antibody before treatment (P < 0.05 control versus TNF-alpha).

CONCLUSIONS

In vitro, MAdCAM-1 can be induced on colon endothelial cells by TNF-alpha stimulation and may represent a useful model to study microvascular injury in the large intestine.

Breast Milk-Derived Antigen-Specific CD8+ T Cells: An Extralymphoid Effector Memory Cell Population in Humans

Although mouse studies have demonstrated the presence of an effector memory population in nonlymphoid tissues, the phenotype of human CD8(+) T cells present in such compartments has not been characterized. Because of the relatively large number of CD8(+) T cells present in breast milk, we were able to characterize the phenotype of this cell population in HIV-infected and uninfected lactating women. CMV, influenza virus, EBV, and HIV-specific CD8(+) T cells as measured by the IFN-gamma ELISPOT and MHC class I tetramer staining were all present at greater frequencies in breast milk as compared with blood. Furthermore, a greater percentage of the breast milk CD8(+) T cells expressed the intestinal homing receptor, CD103, and the mucosal homing receptor CCR9. Breast milk T cells were predominantly CD45RO(+)HLADR(+) and expressed low levels of CD45RA, CD62L, and CCR7 consistent with an effector memory population. Conversely, T cells derived from blood were mainly characterized as central memory cells (CCR7(+)CD62L(+)). These results demonstrate a population of extralymphoid CD8(+) T cells with an effector memory phenotype in humans, which could contribute to enhanced local virologic control and the relative lack of HIV transmission via this route.