Shedding and enrichment of the glycolipid-anchored complement lysis inhibitor protectin (CD59) into milk fat globules.

Protectin (CD59) is a glycolipid-anchored inhibitor of the membrane attack complex (MAC) of human complement (C) that protects blood cells, endothelial cells and various epithelial cells from C-mediated lysis. Because of its activities protectin is a candidate molecule for use in the treatment of paroxysmal nocturnal haemoglobinuria or conditions where MAC causes tissue damage. Soluble, phospholipid-free forms of protectin have been isolated from human urine and produced in recombinant form, but they have only a relatively weak C lysis-inhibiting activity. In the present study we have looked for functionally active protectin in human breast milk. Milk is rich in fat droplets, milk fat globules (MFG), that are enveloped in a plasma membrane derived from secretory cells of the mammary gland. The membranes of MFG contain a variety of glycoproteins expressed by the mammary epithelial cells. Both immunofluorescence and immunoblotting analysis demonstrated that protectin was strongly expressed on human MFG. In sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, MFG protectin (CD59M) appeared as distinct bands with apparent molecular weights of 19,000-23,000 MW, similar to protectin extracted from MCF7 breast carcinoma cells. CD59M in breast milk was functionally active and had a glycophospholipid anchor, as judged by its ability to incorporate into guinea-pig erythrocytes and inhibit their lysis by human complement. These results indicate that functionally active protectin becomes enriched in MFG and imply that secretion of glycophospholipid-anchored molecules, e.g. into cow milk and colostrum, could be exploited as a means of producing bioactive molecules that need to be targeted into cell membranes.     

Anti-complement activities of human breast-milk

OBJECTIVE AND DESIGN: It has long been observed that the human milk possesses significant anti-inflammatory properties, while simultaneously protecting the infant against many intestinal and respiratory pathogens. There is, however, a paucity of information on the degree and extent of this anti-inflammatory activity. In the present study, the inhibitory effects of different fractions of human milk on serum complement activity were analysed. MATERIALS AND METHODS: Colostrum and milk samples from healthy voluntary lactating donors at different postpartum ages were obtained and pooled normal human serum was used as source of complement in a modified CH50 assay. Inherent complement activity in human milk was also investigated by measuring the deposition of an activated C3 fragment on a serum-sensitive bacteria, and by haemolytic assays. RESULTS: Most whole- and defatted-milk samples consistently showed a dose-dependent inhibition of the serum complement activity. This inhibition was greater in mature milk compared to transitional milk samples. It was enhanced by inactivation of milk complement, and diminished by centrifugation of milk samples, which partly removed fat and larger protein components including casein micelles. Inherent complement activity in human milk was also demonstrated by haemolysis of sensitised sheep erythrocytes and deposition of C3 fragments on solid-phase bacteria. These activities were highest in the colostrum and gradually decreased as lactation proceeded. CONCLUSION: Several natural components abundant in the fluid phase of the human breast-milk have been shown to be inhibitors of complement activation in vitro. Their physiological significance probably reside in their ability to prevent inflammatory-induced tissue damage of the delicate immature gastrointestinal tract of the new-born as well as the mammary gland itself, which may arise from ongoing complement activation.     

Mucosal immunity of the mammary gland and immunology of mother/newborn interrelation

Mammary gland is assumed to function as a part of the common mucosal immune system. Lymphocytes observed in the mammary gland derived their origin from precursor immunocompetent cells presented in BALT and GALT. In relation to local immunity of the other sites of the mucosal membranes, lymphocytes homing to the mammary gland are regulated by lactogenic hormones. The other peculiarity of the mammary gland mucosal immunity is a direction of the milk protective factors. The secretory products of lactating mammary gland provide a protection not for own organism, but for newborn infant. The human neonates are essentially devoid of differentiated mechanisms of the secretory immunity. The low IgA level and high free Sc level in newborn secretions reflect the immaturity of the mucosal immunity in the neonatal period. But some evidences suggest the activation and fast maturation of newborn mucosal immunity. There were shown the sharp rises of IgA levels in different newborn's secretions during the neonatal period. Using as an object for the study on the neonatal mucosal immunity the newborn mammary gland, we detected the higher level of Ia-positive cells in neonatal milk in relation to maternal milk, in spite of the low level of Ia-positive cells in newborn's blood. Local immunity seems to function, at least partially, independently on systemic functions in neonates. Significant influence on the development of newborn mucosal immunity exerts maternal milk. The circumstantial evidences support the promoting effect of the human milk on the SIgA synthesis by newborn mucosal membranes. It is impossible to exclude the feasibility of antiidiotypic antibodies presented in human milk actively immunize offspring. At the same time, numerous immunosuppressive factors were found in colostrum. It seems that these factors can protect the newborn immune system against overstimulation by large number of environmental antigens. Human colostrum and milk provide also to neonate numerous soluble and cellular factors of passive immunization. Thus, we can say that human milk serve as a connection link between maternal and newborn immune system, and the main role in mother/newborn interrelations plays the local immunity.     

成人下颌下腺内瘦素和瘦素受体的表达及意义

目的 观察成人下颌下腺内瘦素和瘦素受体的表达和分布。方法 HE染色法和免疫组织化学SABC法。结果 成人下颌下腺内闰管、纹状管和部分小叶间导管上皮细胞呈瘦素及瘦素受体免疫阳性反应，免疫反应产物分布于导管上皮细胞胞质内，细胞核呈阴性反应。结论 成人下颌下腺内有瘦素和瘦素受体表达，可能参与调节胃肠功能及下颌下腺自身的分泌活动。     

Microarray analysis of human milk cells: persistent high expression of osteopontin during the lactation period

To continue the search for immunological roles of breast milk, cDNA microarray analysis on cytokines and growth factors was performed for human milk cells. Among the 240 cytokine-related genes, osteopontin (OPN) gene ranked top of the expression. Real-time PCR revealed that the OPN mRNA levels in colostrum cells were approximately 100 times higher than those in PHA-stimulated peripheral blood mononuclear cells (PBMNCs), and 10 000 times higher than those in PB CD14(+) cells. The median levels of OPN mRNA in early milk or mature milk cells were more than three times higher than those in colostrum cells. Western blot analysis of human milk showed appreciable expression of full-length and short form proteins of OPN. The concentrations of full-length OPN in early milk or mature milk whey continued to be higher than those in colostrum whey and plasma as assessed by ELISA. The early milk (3-7 days postpartum) contained the highest concentrations of OPN protein, while the late mature milk cells (1 years postpartum) had the highest expression of OPN mRNA of all the lactating periods. The results of immunohistochemical and immunocytochemical staining indicated that OPN-producing epithelial cells and macrophages are found in actively lactating mammary glands. These results suggest that the persistently and extraordinarily high expression of OPN in human milk cells plays a potential role in the immunological development of breast-fed infants.     

人奶、牛奶和新生儿配方奶中表皮生长因子含量

目的:比较不同来源新生儿用奶中表皮生长因子(EGF)含量以及母乳EGF含量与新生儿成熟度的相关性。方法:应用放射免疫分析法测定了57份人初乳、4种新鲜牛奶和8种基于牛奶的新生儿配方奶的EGF含量。结果:早产儿乳中EGF含量最高,其次是足月儿乳,母乳EGF含量与新生儿胎龄和出生体重呈负相关;新鲜牛奶的EGF水平(16.6±3.8) nmol/L与足月儿乳相当;非水解蛋白质配方奶中EGF含量较低,水解蛋白质配方奶的EGF浓度在可测范围之下。结论:早产儿乳中EGF的高含量可能代表着一种与早产儿加速生长发育相适应的代偿机制。配方奶中的EGF不足甚至缺乏,不宜应用于消化系统发育不完善或胃肠道受损的新生儿。     

Lymphocyte homing and Ig secretion in the murine mammary gland

In mice the majority of the immunoglobulins (Ig) in milk belongs to the IgA class. Prior to its transepithelial transportation into the milk, dimeric IgA (dIgA) is bound to the transmembrane form of the secretory component or polymeric Ig receptor (SC/pIgR). The latter is synthesized in the epithelial cells lining the ducts and alveoli of the mammary gland. A candidate for playing the role of adhesion molecule to primed lymphocytes present in the murine mammary gland might be the mucosal addressin cell adhesion molecule-1 (MAdCAM-1). We studied the correlation between the levels of IgA in colostrum and milk, the number of IgA producing plasma cells in the mammary gland and the expression of MAdCAM-1 in mammary gland endothelial cells during pregnancy and lactation. The relation between the IgA levels in the milk and the expression levels of pIgR in mammary gland epithelial cells was also investigated. We found that the expression of MAdCAM-1 and pIgR starts in early-mid pregnancy; the number of IgA-producing plasma cells and the IgA concentration in milk increase from early lactation onwards. The MAdCAM-1 expression declines during lactation whereas the pIgR levels and IgA-producing plasma cell numbers rise until the end of lactation. Because the MAdCAM-1 level starts to rise several days before the rise of the IgA-producing plasma cell level, MAdCAM-1 cannot be the rate determining factor governing extravasation of primed B cells to the mammary gland. We also conclude that the pIgR is present in sufficient amounts to enable increasing S-IgA secretion into the milk during lactation.     

Expression of Complement Regulatory Proteins on Human Eggs and Preimplantation Embryos

PROBLEM : To investigate the relation between the complement system and reproduction, expression of complement regulatory proteins (C3b receptors and inhibitor of the membrane attack complex) were screened on unfixed human eggs and preimplantation embryos. METHODS : Unfixed unfertilized oocytes and preimplantation embryos obtained from an in vitro fertilization program were stained by indirect immunofluorescence using monoclonal antibodies raised against membrane cofactor protein, (MCP or CD46), decay accelerating factor (DAF or CD55), protectin (CD59), human C3b/C4b receptor (CR1 or CD35), and major histocompatibility complex class I antigen (MHC class I). RESULTS : CD55 and CD59 were both expressed by the plasma membrane of unfertilized oocytes and pre-implantation embryos. CD46 was not expressed by unfertilized oocytes but appeared at the 6-to-8 cell stage embryo when human gene expression first occurs. CD35 and MHC class I antigens were not expressed at all on oocytes and preimplantation embryos. CONCLUSIONS : Selective expression of complement regulatory proteins (DAF and protectin) associated with the lack of MHC class I antigens may represent an immune protective mechanism by which human oocytes and preimplantation embryos escape complement-mediated damage during their travel through the female genital tract. Furthermore, participation of these complement regulatory proteins including MCP in cell to cell interaction during fertilization and/or implantation cannot be excluded.     

Enhanced expression of decay-accelerating factor and CD59/homologous restriction factor 20 in intestinal metaplasia, gastric adenomas and intestinal-type gastric carcinomas but not in diffuse-type carcinomas

AIMS: Variable expression of the complement regulatory proteins, decay-accelerating factor, CD59/homologous restriction factor 20 (HRF20) and membrane cofactor protein has been shown in human gastrointestinal malignancies, but their expression in gastric cancer has not been fully described. Thus, we immunohistochemically defined the distribution of these proteins in human normal gastric mucosa, intestinal metaplasia, adenomas and gastric cancers. METHODS AND RESULTS: Gastric tissues were obtained by endoscopic biopsy or surgical resection and stained with mouse monoclonal antibodies to decay-accelerating factor, CD59/HRF20, and membrane cofactor protein. In the normal gastric mucosa, membrane cofactor protein was diffusely stained on the basolateral surface of epithelial cells, whereas the expression of decay-accelerating factor and CD59/HRF20 was inconspicuous. In intestinal metaplasia, adenoma and intestinal-type gastric carcinoma cells, decay-accelerating factor and HRF20 were intensely stained on the apical surface; membrane cofactor protein retained its location on the basolateral surface. In diffuse-type gastric carcinomas, the expression of decay-accelerating factor, CD59/HRF20 was lost, but membrane cofactor protein was present on the tumour cell surface. CONCLUSIONS: These findings suggest that membrane cofactor protein plays a primary role in the regulation of complement activation in normal and neoplastic gastric cells and that the expression pattern of the complement regulatory proteins is closely related to gastric carcinoma development.     

Immunohistochemical Localization of C9 Neoantigen and the Terminal Complement Inhibitory Protein CD59 in Human Endometrium

PROBLEM : Human endometrium expresses complement components, receptors, and regulatory proteins, many of which appear to be expressed in a hormone-dependent manner. Whether terminal complement components are also present in the endometrium is unknown. CD59, a broadly expressed protein that blocks association of C9 with C8 in the membrane attack complex, is localized in reproductive tissue to human spermatozoa, seminal plasma, amniotic fluid, and placenta. The present study examines human endometrium for the presence of CD59 and terminal complement proteins. METHOD : Endometrial biopsies were obtained from six normal women from various phases of the menstrual cycle and analyzed by immunohistochemistry, using MEM-43 anti-human CD59 and anti-human SC5b-9 murine monoclonal antibodies and the immunoperoxidase technique. RESULTS : Both CD59 protein and SC5b-9 (C9 neoantigen) were demonstrated to be present in endometrial glandular epithelium throughout the menstrual cycle. No specific staining was demonstrated in the stromal compartment. CONCLUSION : CD59 protein and terminal complement proteins are expressed in glandular epithelial cells of normal human endometrium, in both proliferative and luteal phases, suggesting that expression is not hormonally dependent. These analyses further support the presence of a functionally active complement system in normal human endometrium.     

Identification of the Complement Regulatory Proteins CD46, CD55, and CD59 in Human Fallopian Tube,Endometrium, and Cervical Mucosa and Secretion

PROBLEM : Complement lytic activity has been demonstrated, and a potential for its activation is present in human cervical and tubal secretions and in the endometrium. This necessitates the presence of regulatory mechanisms for protection of the sperm and the implanting allogeneic conceptus in the female genital tract. Complement regulatory proteins demonstrated on sperm and in seminal fluid have been attributed such a role. It is however likely that additional protection is required for a successful conception and implantation to take place. This lead us to investigate the distribution of the complement regulatory factors in cervical mucus and mucosa, uterine endometrium, and fallopian tube. METHOD : Endometrium and cervical mucosa were obtained from patients undergoing hysterectomy for benign conditions, and specimens were selected from different stages of the menstrual cycle. Fallopian tubes were obtained from patients submitted for sterilization, while cervical mucus was aspirated from volunteers undergoing gynecological examination. Immunohistochemistry was performed on all tissue samples, using monoclonal antibodies to membrane cofactor protein (MCP), decay accelerating factor (DAF), CD59 and complement receptor 1 (CR1). Western blot analysis was performed on cervical mucus under nonreducing conditions. RESULTS : MCP, DAF, and CD59 were found to be expressed in human endometrium and fallopian tube. No variation in expression was detected throughout the menstrual cycle. CR1 was not expressed. Soluble forms of DAF and CD59 were found to be present in cervical mucus. CONCLUSION : The complement regulatory proteins MCP, DAF, and CD59 are expressed throughout the female genital tract, and may thus play an important role in protecting the traversing sperm and implanting blastocyst from complement mediated damage.     

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.     

Changes in the cytologic distribution of heparin/heparan sulfate interacting protein/ribosomal protein L29 (HIP/RPL29) during in vivo and in vitro mouse mammary epithelial cell expression and differentiation.

HIP/RPL29 is a small, highly basic, heparin/heparan sulfate interacting protein identical to ribosomal protein L29 and present in most adult epithelia. In the present study, we show that mouse HIP/RPL29 is ubiquitously present in adult mammary epithelia and is significantly increased during pregnancy and lactation. We observed for the first time that HIP/RPL29 intracellular expression and distribution varies, depending on the growth/differentiation state of the luminal epithelium. HIP/RPL29 was detected at low levels in mammary glands of virgin animals, increased markedly during lactation, and was lost again during involution. HIP/RPL29, preferentially found in the expanded cytoplasm of mature epithelial cells secreting milk, is present also in the nucleus of proliferating and differentiating ductal and alveolar elements. We used COMMA-D cells as an in vitro model for mammary-specific differentiation and examined similar intracellular redistribution of HIP/RPL29 associated with functional differentiation. However, no changes in HIP/RPL29 expression levels were detected in response to lactogenic hormones. Finally, the cellular distribution of HIP/RPL29 in both nuclear and cytoplasmic compartments was confirmed by transfecting a normal mammary epithelial cell line, NMuMG, with a fusion protein of HIP/RPL29 and EGFP. Collectively, these data support the idea that HIP/RPL29 plays more than one role during adult mammary gland development.     

Natural Polyreactive IgA and IgM Autoantibodies in Human Colostrum

Secretory antibodies against bacteria and viruses in human colostrum and milk are known to be important protective factors for the breast-fed infant. The authors have shown by enzyme immunoassay that colostrum contains IgA and IgM antibodies to a number of autoantigens: native DNA, actin, myosin, myoglobin, laminin, transferrin and thyroglobulin. These antibodies were polyspecific—those with anti-DNA reactivity immunopurified on a DNA-cellulose affinity column bound to a panel of self- and environmental antigens. The levels of natural autoantibodies in the immunoglobulin fraction of human colostrum were 3–10 times lower (when presented as antibody activity per μg of immunoglobulin) than in the immunoglobulin fraction of serum. The biological significance of the presence of B cells with autoantibody specificity in the mammary gland and of natural autoantibodies in colostrum and milk is not clear. It has been suggested that self-reacting autoantibodies in serum play a major role in the selection of the pre-immune B-cell repertoire and in the maintenance of the immune homeostasis. The authors hypothesize that the natural autoantibodies in colostrum and milk may contribute to the selection process of physiological repertoire during the early postnatal period in breast-fed infants. This could explain the lower frequency of allergic, inflammatory and autoimmune diseases and lymphomas which is seen in their later life when compared with that observed in children who have been formula-fed after birth.     

Increased immunoglobulin A levels in milk by over-expressing the murine polymeric immunoglobulin receptor gene in the mammary gland epithelial cells of transgenic mice

The polymeric immunoglobulin receptor (pIgR) transports dimeric immunoglobulin A (dIgA) across the epithelial cell layers into the secretions of various mucosal and glandular surfaces of mammals. At these mucosal sites, such as the gastrointestinal tract, respiratory tract, urogenital tract and the mammary glands, dIgA protects the body against pathogens. The pIgR binds dIgA at the basolateral side and transports it via the complex mechanism of transcytosis to the apical side of the epithelial cells lining the mucosa. Here, the extracellular part of the receptor is cleaved to form the secretory component (SC), which remains associated to dIgA, thereby protecting it from degradation in the secretions. One pIgR molecule transports only one dIgA molecule (1 : 1 ratio) and the pIgR is not recycled after each round of transport. This implies that the amount of available receptor could be a rate-limiting factor determining both the rate and amount of IgA transported per cell and therefore determining the total IgA output into the lumen or, in case of the mammary gland, into the milk. In order to test this hypothesis, we set up an in vivo model system. We generated transgenic mice over-expressing the murine pIgR gene under lactogenic control, by using a milk gene promoter, rather than under immunological control. Mice over-expressing the pIgR protein, in mammary gland epithelial cells, from 60- up to 270-fold above normal pIgR protein levels showed total IgA levels in the milk to be 1.5-2-fold higher, respectively, compared with the IgA levels in the milk of non-transgenic mice. This indicates that the amount of pIgR produced is indeed a limiting factor in the transport of dIgA into the milk under normal non-inflammatory circumstances.     

Redistribution of the sheep neonatal Fc receptor in the mammary gland around the time of parturition in ewes and its localization in the small intestine of neonatal lambs

Maternal immunity is mediated exclusively by colostral immunoglobulins in ruminants. As the neonatal Fc receptor (FcRn) is suggested to be involved in the transport of immunoglobulin G (IgG) in the mammary gland, we cloned this receptor from sheep and analysed its expression in the mammary gland around the time of parturition and also in the small intestine from the newborn lamb. FcRn heavy-chain mRNA was detected (by using in situ hybridization) exclusively in the acinar and ductal epithelial cells in mammary gland biopsies both before and after parturition. Immunohistochemistry revealed that the cytoplasm of the epithelial cells of the acini and ducts in the mammary gland biopsies stained homogeneously before parturition. A remarkable difference was observed in the pattern after lambing, where the apical side of the cells was strongly stained. The presence of the FcRn in the acinar and ductal epithelial cells of the mammary gland, and the obvious change in distribution before and after parturition, indicate that the FcRn plays an important role in the transport of IgG during colostrum formation in ruminants. Immunohistochemical analysis detected a strong apical and a weak basal FcRn signal in the duodenal crypt cells of a neonatal lamb, which have been previously demonstrated to secrete IgG1 in newborn ruminants. The FcRn was not detected in the duodenal enterocytes, which absorb intact IgG from the colostrum in a non-specific manner. These data suggest that FcRn is involved in IgG1 secretion in ruminant epithelial cells.     

Sinus‐like dilatations of the mammary milk ducts,Ki67 expression,and CD3‐positive T lymphocyte infiltration,in the mammary gland of wild European rabbits during pregnancy and lactation

Sinus‐like dilatations of the mammary duct are recognisable in the mammary gland of pregnant and lactating wild European rabbits. These dilatations exhibit a bilaminar epithelial lining, with luminal epithelial cells expressing basal and lateral E‐cadherin. Occasional binucleated mammary epithelial cells are present in the luminal layer. Underlying the luminal epithelial cells is a basal layer of cytokeratin 14‐positive cells, supported by a thin layer of fibrous tissue. Multi‐segmental epithelial proliferation, as indicated by Ki67 expression, is apparent in the luminal epithelial cells, suggesting a capacity for division during pregnancy and lactation. CD3‐positive T lymphocytes are present both intraepithelially, suggesting exocytosis, and in foci subjacent to the ductular epithelium. We consider that sinus‐like dilatations of the mammary duct may have the potential to give rise to a subset of the mammary gland neoplasms classified as ductal in origin. Milk accumulation in these sinus‐like dilatations is likely to provide a niche for bacterial replication in cases of mastitis in rabbits. These structures are an important component of the innate immune system of the mammary gland, both as a physical barrier and as an interface between the milk and mammary immune cells.     

The function and affinity maturation of HIV-1 gp120-specific monoclonal antibodies derived from colostral B cells

Despite the risk of transmitting HIV-1, mothers in resource-poor areas are encouraged to breastfeed their infants because of beneficial immunologic and nutritional factors in milk. Interestingly, in the absence of antiretroviral prophylaxis, the overwhelming majority of HIV-1-exposed, breastfeeding infants are naturally protected from infection. To understand the role of HIV-1 envelope (Env)-specific antibodies in breast milk in natural protection against infant virus transmission, we produced 19 HIV-1 Env-specific monoclonal antibodies (mAbs) isolated from colostrum B cells of HIV-1-infected mothers and investigated their specificity, evolution, and anti-HIV-1 functions. Despite the previously reported genetic compartmentalization and gp120-specific bias of colostrum HIV Env-specific B cells, the colostrum Env-specific mAbs described here demonstrated a broad range of gp120 epitope specificities and functions, including inhibition of epithelial cell binding and dendritic cell-mediated virus transfer, neutralization, and antibody-dependent cellular cytotoxicity. We also identified divergent patterns of colostrum Env-specific B-cell lineage evolution with respect to crossreactivity to gastrointestinal commensal bacteria, indicating that commensal bacterial antigens play a role in shaping the local breast milk immunoglobulin G (IgG) repertoire. Maternal vaccine strategies to specifically target this breast milk B-cell population may be necessary to achieve safe breastfeeding for all HIV-1-exposed infants.     

Human breast milk T lymphocytes display the phenotype and functional characteristics of memory T cells

Naive (unsensitized) and memory (antigen-primed) T cells can be phenotypically distinguished on the basis of the high or low intensity with which they express a number of immunologically relevant lymphocyte membrane antigens, including CD45R, CDw29, UCHL1, LFA-1, LFA-3, CD2 and Pgp-1. Here we report that in contrast to the two major T cell subsets found in the blood, milk T lymphocytes are almost exclusively composed of the one which exhibits the CD45Rlow, CDw29, UCHL1, LFA-1high memory T cell phenotype. In addition, while milk and autologous blood cells expressed similar levels of CD3 surface antigens, CD2 and ICAM-1 expression was approximately twofold greater on the milk T lymphocytes. This agrees with the finding that whereas colostrum T cells respond poorly to PHA, they proliferate and produce interferon-gamma normally when stimulated with either the anti-CD3 or anti-CD2 monoclonal antibodies. The selective colonization of the mammary gland during lactation by a population of T lymphocytes which displays the phenotype and functional characteristics of memory T cells may be one of the mechanisms whereby the suckling infant benefits form its mother's immunological experience.     

Molecular properties of poliovirus neutralizing antibodies in human colostrum and milk

Summary The poliovirus neutralizing antibodies of human colostrum and milk have been identified as belonging to the beta₂A class of immunoglobulins. This has been done by isolating this fraction (which is the major one) of the immunoglobulins of colostrum and milk and by showing that the antibody activity was localized in it. The isolation of the beta₂A globulins was performed by a combination of preparative electrophoresis or gel-filtration and DEAE column chromatography; the purity of the resulting fraction was checked by immunodiffusion against suitable antisera.In contrast with the findings in colostrum and milk the bulk of the poliovirus neutralizing antibodies in the serum of the same women, appeared to be localized in the gamma₂ globulins, with only minor amounts in the beta₂A; it is therefore considered likely that the beta₂A globulins (and antibodies) are actively secreted by the mammary gland. In consideration of the fact that beta₂A antibodies have a strong affinity for binding to the cells, it is possible that the beta₂A poliovirus neutralizing antibodies of human colostrum and milk have some importance in protecting the cells of the alimentary tract of the newborn from the virus infection.