Armond S. Goldman

Host resistance factors in human milk

This paper discusses the nature of host resistance factors in human milk and epidemiologic studies regarding infections and mortality rates in breastfed and nonbreastfed babies. The defense factors and their proposed modes of action are: 1) a growth enhancer of lactobacilli, which interferes with intestinal colonization of enteric pathogens; 2) antistaphylococcal factors, which inhibit staphylococci; 3) secretory IgA and other immunoglobulins, which protect the gut and respiratory tract; 4) C4 and C3 (complement components; C3 fragments have opsonic, chemotactic, and anaphylatoxic activities); 5) lysozome, lysis of bacterial cell wall; 6) lactoperoxidase, killing of streptococci; 7) lactoferrin, kills microorganism by chelating iron, and 8) macrophages and lymphocytes, phagocytosis and cell-mediated immunity. Although it can be postulated that the breastfed infants resistance to infection would be superior on account of the greater presence of these factors in human milk compared to cows milk, little is known about the effects of these defense factors on the infant. Epidemiologic studies have reported on the lower morbidity and mortality rates of breastfed infants as compared to bottlefed infants. Other studies have focused on the protective effects of human milk upon the infant, but these have been inconclusive. In countries with poor sanitation and high infection rates, the incidence of bacterial infections is lowest in breastfed infants. The advantages of human milk however are difficult to demonstrate in societies with high standards of sanitation and low infection rates. Infection and mortality rates in infants have in fact declined in developed countries as the practice of breastfeeding declined. Until it is established that immunity to common pathogens is transmitted to the infant by human milk, it will not be known whether human milk does have protective effects.

Breastfeeding: maintaining an irreplaceable immunological resource

Breastfeeding — the main source of active and passive immunity in the vulnerable early months and years of life — is considered to be the most effective preventive means of reducing the death rate of children under five. Given this, one must wonder why it has slipped quietly down the priorities of the global health and development agendas. In this era of public–private partnerships, can its role as an irreplaceable immunological resource help keep it at the top of global agendas?

Interleukin-10 in human milk.

ABSTRACT: The concentrations of immunoreactive IL-10 in the aqueous fraction of 20 specimens of human milk obtained during the first 80 h of lactation and stored at –60°C ranged from 66 to 9301 pg/mL (mean ± SD, 3304 ± 3127 pg/mL). IL-10 was present also in the lipid layer of milk. Gel filtration revealed that IL-10 was located in a high molecular weight fraction, where certain other cytokines in human milk have been found. In addition, immunoreactive IL-10 in milk increased after treatment with sodium taurocholate. Bioactive IL-10 was demonstrated by the finding that human milk inhibited [3H]thymidine uptake by human blood lymphocytes and that inhibition was partly overcome by concomitant incubation with antibodies to human IL-10. IL-10 mRNA but no protein product was found in cultured human mammary epithelial cells. Some IL-10 was associated with preparations of human milk leukocytes, but the data did not suggest that the cells were producing the cytokine. Bioactive IL-10 in a possible protected compartment suggests that IL-10 in human milk may have immunomodulating, antiinflammatory effects on the alimentary tract of the recipient infant.

Anti‐inflammatory Properties of Human Milk

ABSTRACT. An hypothesis was developed which predicts that human milk protects against infections of the alimentary tract of the breast‐fed infant by non‐inflammatory mechanisms. Human milk is poor in the initiators and mediators of inflammation and rich in anti‐inflammatory agents. Furthermore, many of the anti‐inflammatory agents are comparatively resistant to digestive enzymes and therefore might be expected to remain active in the gastrointestinal tract of the recipient. Further studies of these factors in in vivo models will be required to validate the hypothesis.

Decreased Interleukin-10 Production by Neonatal Monocytes and T Cells: Relationship to Decreased Production and Expression of Tumor Necrosis Factor-α and Its Receptors

The production of IL-10 by human neonatal blood mononuclear leukocytes(BML) stimulated with lipopolysaccharide (LPS), tumor necrosis factor-α(TNF-α), antibodies to CD3, or phorbol 12-myristate 13-acetate (PMA) was measured. The production of IL-10 by neonatal BML cultured with LPS or TNF-α was ≈20 and ≈15%, respectively, of adult BML. The combination of human recombinant TNF-α and LPS failed to augment IL-10 production in neonatal BML. The decreased production of IL-10 by neonatal leukocytes was not due to an autocrine feedback mechanism because only low concentrations of IL-10 were found in newborn sera. A connection with TNF-α could not be ruled out, because TNF-α production by LPS-stimulated newborn BML and the expression of TNF-α receptors on newborn monocytes were reduced. Mean ± SD of concentrations of IL-10 in supernatants from adult and neonatal BML after stimulation with antibodies to human CD3 for 48 or 72 h were 914 ± 386 and 178 ± 176 pg/mL, respectively (p < 0.0001). In experiments with enriched populations of neonatal T cells, the addition of PMA failed to augment IL-10 production. This suggested that newborn T cells may be in a different state of activation than adult T cells Thus, IL-10 production in neonatal monocytes and T cells is reduced and this study suggests that the reduction may be secondary in part to regulatory processes involving TNF-α and its receptors.

Evolution of immunologic functions of the mammary gland and the postnatal development of immunity

Physiologic delays in production of immune factors occur in mammals including Homo sapiens. This finding is counter to a basic tenet of biologic evolution, because such delays increase the risk of infections. The disadvantage is, however, offset by defense factors in milk of the species in whom the developmental delay occurs. Reciprocal relationships between the production of immune factors by the lactating mammary gland and the production of those defense agents during early infancy are found in all investigated mammalian species. Thus, the evolution of these processes is closely related. Certain immunologic components of milk are highly conserved, whereas others vary according to the species. The variations most likely evolved by genetic mutations and natural selection. In addition, the immune composition of mammalian milks is associated with developmental delays in the same immunologic agents. Furthermore, most closely related mammals, such as humans and chimpanzees, are most similar in the defense agents in their milks and the corresponding developmental delays in their immune systems. Defense factors in human milk include antimicrobial agents (secretory IgA, lactoferrin, lysozyme, glycoconjugates, oligosaccharides, and digestive products of milk lipids), antiinflammatory factors (antioxidants, epithelial growth factors, cellular protective agents, and enzymes that degrade mediators of inflammation), immunomodulators (nucleotides, cytokines, and antiidiotypic antibodies), and leukocytes (neutrophils, macrophages, and lymphocytes). Because of a lack of geographic/ethnic variation in the immunologic composition of human milk and corresponding immunologic delays in infants, these evolutionary processes seem stable. This is supported by investigations of diverse populations that indicate that this evolutionary outcome is highly beneficial to human infants.

Tumor necrosis factor-α in human milk

ABSTRACT: We previously demonstrated that certain biologic activities in human milk were partially blocked by antibodies directed against human tumor necrosis factor-α (TNF-α). In this study, immunochemical methods were used to verify the presence of TNF-α in human milk obtained during the first few days of lactation. Gel filtration revealed the presence of TNF-α by RIA in molecular weight fractions between 80 and 195 kD. TNF-α could not be detected consistently by conventional Western blotting or cytotoxic assays. Although immunoreactive bands were detected by a Western blot-125I protein A technique in TNF-α-positive fractions from gel filtration, those bands proved to be nonspecific. TNF-α in milk was reliably quantified by the competitive RIA. Those studies revealed that the concentrations of TNF-α in milk were 620 ± 183 pg/mL. Although RNA to TNF-α was detected in milk leukocytes by Northern blotting, little TNF-α was found in those cells before or after stimulation with N-formyl-l-methionyl-l-leucyl-l-phenylalanine or 4β-phorbol-12β-myristate-13α-acetate. The origin of this cytokine in human milk remains unclear. Nevertheless, this study suggests that TNF-α is present in early human milk in sufficient quantities to exert possible biologic effects upon the mammary gland of the mother or the immune system of the infant.

Cytokines in human milk: Properties and potential effects upon the mammary gland and the neonate

Epidemiologic and immunologic studies of breastfed and nonbreastfed infants and investigations of certain biologic activities in human milk led to the identification of immunomodulating agents in human milk. Among them were the cytokines interleukin-1β (IL-1β); IL-6, IL-8, IL-10, granulocyte-colony stimulating factor, macrophage-colony stimulating factor (M-CSF), tumor necrosis factor-α, interferon-γ, epithelial growth factor (EGF), transforming growth factor-α (TGF-α), and TGF-β2. Inteferon-γ may originate from T cells in milk; EGF, TGF-α, TGF-β, M-CSF, IL-6, and IL-8 may be produced by mammary gland epithelium. Based upon their known functions, we hypothesize that cytokines influence the development and immunologic function of the mammary gland and the neonate. Thosein vivo functions remain to be defined by future investigations.

Cytokines, chemokines, and colony-stimulating factors in human milk: the 1997 update.

Epidemiologic studies conducted over the past 30 years to investigate the protective functions of human milk strongly support the notion that breast-feeding prevents infantile infections, particularly those affecting the gastrointestinal and respiratory tracts. However, more recent clinical and experimental observations also suggest that human milk not only provides passive protection, but also can directly modulate the immunological development of the recipient infant. The study of this remarkable defense system in human milk has been difficult due to its biochemical complexity, the small concentration of certain bioactive components, the compartmentalization of some of these agents, the dynamic quantitative and qualitative changes of milk during lactation, and the lack of specific reagents to quantify these agents. Nevertheless, a host of bioactive substances including hormones, growth factors, and immunological factors such as cytokines have been identified in human milk. Cytokines are pluripotent polypeptides that act in autocrine/paracrine fashions by binding to specific cellular receptors. They operate in networks and orchestrate the development and functions of the immune system. Several different cytokines and chemokines have been discovered in human milk over the past years, and the list is growing very rapidly. This article will review the current knowledge about the increasingly complex network of chemoattractants, activators, and anti-inflammatory cytokines present in human milk and their potential role in compensating for the developmental delay of the neonate immune system.

Production of interleukin-6 and interleukin-8 by human mammary gland epithelial cells

The production of transforming growth factor-beta 2 (TGF-beta 2), interleukin-1 beta (IL-1 beta), IL-6, IL-8, and tumor necrosis factor-alpha (TNF-alpha) by spontaneously immortalized human mammary gland epithelial cells of non-malignant origin and the effect of prolactin upon the production of those cytokines were investigated. Cells were cultured on plastic with epithelial growth factor, insulin, and hydrocortisone. Cytokines were quantified by enzyme-immunoassays. The cells produced IL-6 and IL-8, but no detectable TGF-beta 2, IL-1 beta, or TNF-alpha. Although prolactin enhanced the uptake of [3H]thymidine, it did not alter the production of cytokines/interleukins. Because of the marked production of IL-8 by mammary epithelium and a past report of TGF activity in human milk, those agents were quantified in human milk. The mean +/- S.D. concentrations of IL-8 and TGF-beta 2 in human milk obtained in the first 3 days of lactation were 3684 +/- 2910 and 130 +/- 108 pg/ml, respectively. Thus, IL-8 and TGF-beta 2 are normal constituents in human milk, and human mammary gland epithelium may be responsible for producing some of the IL-6 and IL-8 in human milk.