|Food and Nutrition Bulletin Volume 17, Number 4, 1996 (UNU Food and Nutrition Bulletin, 1996, 163 pages)|
|Infection and disease|
Lars A. Hanson, Ursula Wiedermann, Rifat Ashraf, Shakila Zaman, Ingegräd Adlerberth, Ulf Dahlgren, Agnes Wold, and Fehmida Jalil
Human milk is a very complex fluid with a number of components and multiple functions. New functions are continually being identified. It is clear that human milk can affect the immune system of the breasfed infant. This results both in enhanced vaccine responses and, at times, down-regulation of other immune reactivities, such as transplant rejection and the risk of developing certain immunologic diseases, such as type I diabetes. Breastfeeding presumably gives the infant the possibility for an optimal immune response by providing good nutrition, including a decreased risk of vitamin A deficiency. The control of the intestinal flora and the anti-inflammatory effects of maternal milk also increase the possibilities for an adequate immune response in the infant. Further study is needed of the roles of idiotypic and anti-idiotypic antibodies, growth factors, cytokines, and various anti-inflammatory factors in the maternal milk in the infant's host defence.
Human milk is a very complex fluid with a multitude of proteins, cells, and other components. Knowledge is continually increasing about the effects of breastfeeding on the infant, including a number of direct and indirect effects on the immune system. Such influences are related to the fact that human milk is rich in various immunologically active factors, in particular the stable antibodies. Secretory IgA (SlgA) protects the mucous membranes of the infant's gastrointestinal and respiratory tracts, where most infections occur . Mother's milk also contains IgG and IgM antibodies, hormones, antioxidants, vitamins, cytokines, growth factors, complement factors, prostaglandins, granulocytes, macrophages, B and T Iymphocytes, and so forth. Many of these milk components not only participate in the support of the infant's host defence but also affect the normal microbiological flora in the gastrointestinal tract. In addition, other tissues and organs, including the immune system, are influenced.
Breastfeeding enhances vaccine responses in the infant and may affect transplantation outcome
A significantly higher salivary SlgA antibody response was obtained in breastfed than in nonbreastfed Italian infants after parenteral vaccination with diphtheria and tetanus toxoids and after oral poliovirus vaccination . Stool SlgA antibodies could not be used to measure the antibody response because of the presence of milk SlgA antibodies in the stool of breastfed infants. Instead, we analysed stool IgM, an isotype that is present at very low levels in maternal milk. The stool IgM response to parenteral tetanus toxoid and oral poliovirus vaccine was significantly higher in the breastfed group. These observations of the secretory antibody increases were obtained in infants 3 and 4 months of age. The infants had been vaccinated according to the ordinary vaccination schedule at 2, 3, and 12 months of age. Between the ages of 21 and 40 months, serum IgG antibodies to diphtheria toxoid and neutralizing serum antibodies to poliovirus were also significantly increased among the breastfed group compared with the formula-fed controls. These observations are in agreement with another study that determined the serum antibody response to the Haemophilus influenzae type b (Hib) polysaccharide capsule in breastfed and nonbreastled children who were vaccinated parenterally with an Hib protein conjugate vaccine .
The explanation for this effect of breastfeeding on the vaccine response is not entirely clear. We favour the hypothesis that at least some of the enhancing effect could be due to the anti-idiotypic antibodies (anti-antibodies) in human milk. We have shown the presence of such anti-antibodies against poliovirus in human milk . In the proper concentration, antiidiotypes can enhance immune responses . Nevertheless, it is not clear how milk immunoglobulins could be taken up by the child, and other explanations are possible. Thus, maternal milk contains nucleotides that might affect the infant's immune response by stimulating lymphocytes].
If breastfeeding is enhancing vaccine responses, one might expect long-term positive effects of breastfeeding on the host resistance of the breastfed infant. In fact, Silfverdahl et al.  found a long-term protective effect of breastfeeding against invasive H. influenzae infections such as meningitis and epiglottitis.
Several early studies suggested that tuberculin sensitivity was transferred via mother's milk [8, 9]. Even if the resulting tuberculin sensitivity in the infant was temporary, the observation suggested that T Iymphocytes present in milk could be transferred to the offspring. This may be the reason why vaccination against bacillus Calmette-Guérin seems to induce a stronger T-cell response in breastfed infants than in non-breastfed infants .
Transfer of milk cells may also result in immunologic tolerance (selectively reduced immune response) in the baby. Thus, a low response to paternal cells can be induced in newborn mice by letting them suckle a foster mother with the same transplantation antigens as their father . This phenomenon may explain why renal transplants from mothers survive longer in offspring they have breastfed than in those they have not breastfed . In premature infant baboons given radioactively labelled human colostral leucocytes, radioactivity accumulated in the gut wall, liver, and spleen . This suggests that the milk cells are really taken up and have the capacity to influence the immune system of the offspring. Such an influence might explain the finding that breastfeeding can decrease the risk of the offspring developing autoimmune type I diabetes later . The risk of type I diabetes determined by genetic factors is 30% to 40%. Nevertheless, the risk of inheritance from the father is two to three times greater than that from the mother. This difference may be at least partially explained by the effect of breastfeeding, which seems to halve the risk. In this connection, it may be added that breastfeeding seems to diminish the risk of developing Iymphomas  and Crohn's disease . This effect remains long after the breastfeeding has been terminated.
Breastfed infants respond to infections with respiratory syncytial virus with more interferon-y (IFN-y) than do non-breastfed infants . The breastfed infants also produce higher total levels of SlgA in the urine than their formula-fed counterparts .
Breastfeeding, nutrition, and immunity
A major cause of undernutrition in poor countries is the frequent infections resulting from inadequate hygiene, with contaminated water, lack of latrines, ineffective vaccination programmes, inefficient primary health care, lack of education, and the like. As shown by Howie  in this Workshop, breastfeeding can effectively prevent many of those infections.
Breastfed infants are usually given extra water during the hot season. Several studies have shown that this is totally unnecessary [20, 21]. Extra water makes babies less thirsty, which causes them to suck less, so that less milk is produced. Therefore, during the hot season, when the risk of infection is highest, the babies will get less milk. We have shown in a study from Pakistan that infants given water have more frequent diarrhoeal attacks and a significant reduction of weight and of head circumference compared with those who are exclusively breastfed . Whereas breastfeeding provides optimal nutrition to the infant, deficient or absent breastfeeding is clearly a risk factor for inadequate nutrition. The subsequent frequent infections add to the undernutrition, which can impair host defence in a number of ways. It is not always clear, however, that these disturbances of the immune system are of clinical relevance.
We have shown that vitamin A deficiency in rats causes a severe immunodeficiency, followed by a greatly reduced capacity to respond to vaccines and to resist infections, such as diarrhoea and septic arthritis [22, 23]. These animals also have severe protein-calorie undernutrition owing to the loss of appetite caused by the lack of vitamin A. When the vitamin deficiency is corrected by giving retinyl palmitate (vitamin A), their immune response normalizes, although their body weight remains some 30% less than normal.
Immunodeficiency in vitamin A-deficient rats is characterized by a 90% reduction of the intestinal SlgA antibody response to an oral cholera vaccine and a similar reduction of IgE antibody responses to soluble proteins. There is also a reduced IgM and IgG antibody production in response to T cell-dependent antigens. In addition, there is an upregulation of certain TH1 activities.
When these animals are colonized orally with a strain of Escherichia coli, the whole gut contains large numbers of bacteria, which translocate and are thus found in the local Iymph glands. The rats get diarrhoea and at the same time show increased levels of IgE antibodies to the colonizing bacteria and a normalization of the SIgA response, possibly owing to an adjuvant effect of the bacteria in the lymph nodes. These observations may be relevant to several unexplained problems with infection among non-breastfed infants in poor countries .
The most common cause of death between 3 and 28 days of age in poor populations in Pakistan is neonatal septicaemia . The causative bacteria most likely originate in the intestinal flora. The subclinical vitamin A deficiency may increase the risk of translocation of intestinal bacteria so that these bacteria reach the bloodstream. The major cause of death after 28 days of age is diarrhoea, and 84% of the deaths occur after prolonged diarrhoea. Again, early subclinical vitamin A deficiency may pave the way for prolonged diarrhoea.
In Pakistan 34% of the mortality in the first two years of life occurs in the first week and 90% in the first six months . Measures to protect infants during this sensitive period of life are therefore crucial. Vitamin A deficiency is common in mothers and infants in our study area in Pakistan (unpublished data), as in many other pans of the developing world. A significant reduction of this early mortality might be attained by giving the mothers vitamin A directly after delivery and ensuring that they start breastfeeding immediately, thus transferring most efficiently both vitamin A and SIgA antibodies.
In a pilot study in a Pakistani village, we have seen the effects of introducing a health programme that involves breastfeeding promotion, improved primary health care, and education of mothers. Infant modality, stunting, and the prevalence of diarrhoea were all decreased by 50% within two years (F. Jalil, personal communication, 1995). It will be of interest to see what supplementation of breastfeeding mothers with vitamin A might do in this setting.
Breastfeeding and the intestinal flora
Other kinds of indirect effects on the infant's host defence presumably follow from the effects of breastfeeding on the intestinal flora. Non-breastfed infants in poor areas are quickly colonized by several potentially pathogenic aerobic bacterial strains, which show a continuous flux in the gut. In contrast, exclusively breastfed Swedish infants show a stable, more slowly developing intestinal flora, dominated among the aerobes mostly by a single strain of E. coli or sometimes Klebsiella . This difference in the diversity of the enterobacterial flora in breastfed and non-breastfed infants has also been seen in other countries in Europe . Certain E. coli may be favoured by breastfeeding, and so is their expression of the adhesin called type 1 fimbriae ,* which, in contrast to other E. coli adhesins, is not associated with virulence. This may be due to the fact that type 1 fimbriae bind directly to mannose residues on phagocytes, which promote phagocytosis . Other adhesins that may function as virulence factors seem to be suppressed by breastfeeding.
It is obvious that various milk factors can prevent adhesion of certain E. coli to host tissues, presumably influencing the immune response. One example is shown in figure 1. Among such anti-adherence substances in milk are SlgA antibodies and various analogues to epithelial receptors that bind Vibrio cholerae, E. coli , V. cholerae enterotoxin , pneumococci, and H. influenzae . Recently, a milk component, presumably a glucosaminoglycan, has been shown to inhibit the binding of human immunodeficiency virus (HIV) to its CD4 receptor on lymphocytes . The continuous exposure of E. coli to milk components in the gut of the breastfed infant induces continuous changes of surface structures presumably tied to decreasing virulence .
Breastfed infants have higher counts of Staphylococcus aureus, S. epidermidis, and enterococci in the gut than nonbreastfed infants [35-37]. In contrast, breastfed infants do not have higher counts of bifido-bacteria, as is often presumed .
It seems likely that the immune response may differ in breastfed infants, who have a stable intestinal flora in which the aerobes are dominated by E. cold of little or no virulence, and non-breastfed infants, who have a variable flora containing various pathogens and who therefore are at high risk of diarrhoea and other infections. It could also be that various milk components modify the exposure to certain antigens or their presentation to the infant's immune system.
Human milk is anti-inflammatory
Mother's milk contains a number of anti-inflammatory factors with anti-oxidant activity that are able to block chemotaxis of granulocytes and inhibit production of free radicals, peroxidase, and so forth . It is possible that these functions may enhance the well-being of the neonate by preventing inflammation. The neonate is colonized with gram-negative bacteria producing endotoxins in the gut that may induce the production of inflammatogenic, catabolic, and appetite-reducing cytokines such as interleukin1 (IL-1), IL-6, and tumour necrosis factor-a (TNF-a). This cytokine production may be prevented by capacities of the breastmilk. which may be one explanation why non-breastfed infants lose significantly more weight during the first week of life than those exclusively breastfed . In this connection, it is interesting that human milk lactoferrin, a major milk protein, can block endotoxin-induced IL-6 release from human cells . On the other hand, a similar effect is obtained with undenatured bovine millk lactoferrin and its bactericidal peptide lactoferricin.
Human milk contains cytokines such as IL-1, TNF-a, IFN-g , IL-6, transforming growth factor-ß (TGF-ß). and IL-10 [42-44]. Cytokine production can be induced from milk cells as well. Thus, the milk T cells can produce IL-2, IL-3, IL-4, IL-10, IFN-g , and TNF-a , and the macrophages can produce IL-1a IL-1p, IL-lra (IL-1 receptor analogue), IL-6, IL-8, and IL-10. It is presently unknown whether all these cytokines, with capacities to strikingly influence immune responses, can also have such effects on the breastfed infant's immune reactivity. It is likely that their presence and potential activities are under strict control. The cytokine-modulating effect of lactoferrin mentioned above may be an example of such a control function.
Our studies have been supported by the Swedish Agency for Research Cooperation with Developing Countries and the Swedish Medical Research Council (no. 215).
A combined discussion of this paper and the paper by Victora can be found after Victora's paper on page 397.
1. Goldblum RM, Hanson LA, Brandtzaeg P. The mucosal defence system. In: Stiem RT, ed. Immunologic disorders in infants and children. 4th ed. Philadelphia, Pa USA: WB Saunders, 1996:159-99.
2. Hahn-Zoric M, Fulconis F. Minoli I, Moro G. Carlsson B. Böttiger M, Räihä N. Hanson LA. Antibody responses to parenteral and oral vaccines are impaired by conventional and low protein formulas as compared to breast-feeding. Acta Paediatr Scand 1990;79:113742.
3. Pabst HF, Spady DW. Effect of breast-feeding on antibody response to conjugate vaccine. Lancet 1990;336: 269-70.
4. Hahn-Zoric M, Carlsson B. Jeansson S. Ekre O. Osterhaus AD, Roberton, DM, Hanson LA. Anti-idiotypic antibodies to poliovirus in commercial immunoglobulin, human serum and human millk. Pediatr Res 1993; 33:47580.
5. Stein KE, Söderström T. Neonatal administration of idiotype or anti-idiotype primes for protection against Escherichia cold K13 infection in mice. J Exp Med 1984;160:1001-11.
6. Carver JD, Pimentel B. Cox Wl, Barness LA. Dietary nucleotide effects upon immune function in infants. Pediatrics 1991;88:359-63.
7. Siliverdahl R. Bodin L, Hugosson S. Garpenholt Ö. Werner B. Esjörner E, Lindqvist B. Olcén P. Protective effect of breastfeeding on invasive Haemophilus inluenzae infection: a case control study in Swedish preschool children (submitted for publication).
8. Ogra SS, Weintraub D, Ogra PL. Immunologic aspects of human colostrum and milk. III. Fate and absorption of cellular and soluble components in the gastrointestinal tract of the newborn. J Immunol 1977;119:245-8.
9. Schlesinger JJ, Covelli HD. Evidence for transmission of lymphocyte response to tuberculin by breast-feeding. Lancet 1977;2:529-32.
10. Pabst H. Grace M, Godel J. Cho H. Spady D. Effect of breastfeeding on immune response to BCG vaccination. Lancet 1989;1:295-7.
11. Deroche A, Nepomnaschy 1, Torello S. Goldman A, Piazzon 1. Regulation of parental alloreactivity by reciprocal F1 hybrids. The role of lactation. J Reprod Immunol 1993;23:235-45.
12. Campbell DA, Lorber Ml, Sweeton JC, Turcotte JG, Niederhuber J. Beer AK. Breast-feeding and maternal-donor renal allografts. Transplantation 1984;37:3404.
13. Jain L, Vidyasagar D, Xantou M, Ghai V, Shimada S. Blend M. In vivo distribution of human milk leukocytes after ingestion by newborn baboons. Arch Dis Child 1989;64:930-3.
14. Dosch HM, Martin JM, Robinson BH, Akerblom HK, Karjalainen J. An immuno basis for disproportionate diabetes risks in children with a type I diabetic mother or father. Diabetes Care 1993;16:949-51.
15. Davis MK, Savitz DA, Grauford B. Infant feeding in childhood cancer. Lancet 1988;2:365-8.
16. Koletzko S. Sherman P. Corey M, Griffiths A, Smith C. Role of infant feeding practices in Crohn's disease in childhood. BMJ 1989;298:1617-8.
17. Chiba Y. Minagawa T. Mito K, Nakane A, Suga K, Honjo T. Nako T. Effect of breast-feeding on responses of systemic interferon and virus-specific Iymphocyte transformation in infants with respiratory syncytial virus infection. J Med Virol 1987;21:7-14.
18. Goldblum RM, Schandler RJ, Garza C, Goldman AS. Human milk feeding enhances the urinary excretion of immunologic factors in low birth weight infants. Pediatr Res 1989;25:184-8.
19. Howie PW. Protective effect of breastmilk against infection. Food Nutr Bull 1996;17:373-83.
20. Almroth SG. Water requirements of breast-fed infants in a hot climate. Am J Clin Nutr 1978;31:1154-7.
21. Ashraf RN, Jalil F. Hanson LA, Karlberg J. Giving water during breastfeeding affects diarrhoeal incidence and early short term growth in a poor environment. Acta Paediatr (in press).
22. Wiedermann U. Dahlgren U. Holmgren J. Hanson LA. Impaired mucosal antibody response to cholera toxin in vitamin Adeficient rats immunized with oral cholera vaccine. Infect Immun 1993;61:3952-7.
23. Wiedermann U. Hanson LA, Kahu H. Dahlgren U. Aberrant Tcell function in vitro and impaired T-cell dependent antibody response in vivo in vitamin A-deficent rats. Immunology 1993;80:581-6.
24. Wiedermann U. Hanson LA, Bremell T. Kahu H. Dahlgren U. Increased translocation of Escherichia cold and development of arthritis in vitamin A deficient rats. Infect Immun 1995;63:3062-8.
25. Khan S. Jalil F. Zaman S. Lindblad BS, Karlberg 1. Early child health in Lahore, Pakistan: X. Mortality. Acta Paediatr Suppl 1993;390:109-17.
26. Adlerberth 1, Carlsson B. de Man P. Jalil F. Khan SR, Larsson P. Mellander L, Svanborg C, Wold AK, Hanson LA. Intestinal colonization with Enterobacteriaceae in Pakistani and Swedish hospital-delivered infants. Acta Paediatr Scand 1991;80:602-10.
27. Orskov F. Biering-Sorensen K. Escherichia cold serogroups in breast-fed and bottle-fed infants. Acta Pathol Microbiol Scand B 1975;83:25-30.
28. Lodinova ZR, Slavikova M, Tlaskalova HH, Alderberth 1, Hanson LA, Wold A, Carlsson B. Svanborg C, Mellander L. The antibody response in breast-fed and non-breast-fed infants after artificial colonization of the intestine with Escherichia cold 083. Pediatr Res 1991; 29:396-9.
29. Bar-Shavit Z. Goldman R. Ofoh 1, Sharon N. Mirelman D. Mannose-binding activity of Escherichia cold a determinant of attachment and ingestion of the bacteria by macrophages. Infect Immun 1980;29:41724.
30. Holmgren J. Svennerholm AM, Ahrén CH. Nonimmunoglobulin factors in milk inhibit bacterial adhesions (haemagglutination) and enterotoxin binding of Escherichia cold and Vibrio cholerae. Infect Immun 1981; 33:136-41.
31. Lagreid A, Kolsto-Otnaess AB. Trace amounts of ganglioside GM1 in human milk inhibit enterotoxins from Vibrio cholerae and Escherichia coli. Life Sci 1987;4:55-62.
32. Andersson B, Porras O, Hanson LA, LaBergard T, Svanborg EC. Inhibition of attachment of Streprococcus pneumoniae and Haemophilus inpuenzae by human milk and receptor oligosaccharides. J Infect Dis 1986;153:232-7.
33. Newburg DS, Viscidi RP, Ruff A, Yolken RH. A human milk factor inhibits binding of human immunodeficiency virus to the CD4 receptor. Pediatr Res 1992;31:22-8.
34. Gothefors L, Olling S, Winberg J. Breastfeeding and biological properties of fecal E. cold strains. Acta Paediatr Scand 1975;64:807-11.
35. Balmer SE, Wharton BA. Diet and faecal flora in the newborn: breastmilk and infant formula. Arch Dis Child 1989;64:1672-7.
36. Lundeqvist B, Nord CE, Winberg J. The composition of the faecal microflora in breastfed and bottle fed infants from birth to eight weeks. Acta Paediatr Scand 1985;74:45-51.
37. Simhon A, Douglas JR, Drasar BS, Soothill JF. Effect of feeding on infants' faecal flora. Arch Dis Child 1982;57:54-8.
38. Wold A, Hanson LA. Defence factors in human milk. Curr Opin Gastroenterol 1994;10:652-8.
39. Goldman AS, Goldblum RM, Thorpe LW, Hanson LA. Antiinflammatory properties of human milk. Acta Paediatr Scand 1986;75:689-94.
40. Rassin DK, Räihä NC, Minoli 1, Moro G. Taurine and cholesterol supplementation in the term infant: responses of growth and metabolism. J Parenter Enteral Nutr 1990;14:3927.
41. Mattsby-Baltzer 1, Roseanu A, Motas C, Elverfors J. Engberg 1, Hanson LA. Lactoferrin inhibits the endotoxin-induced IL6 response in human monocytic cells. Paediatr Res (in press).
42. Bocci V, von Bremen K, Corradeschi F. Franchi F. Luzzi E, Paulesu L. Presence of interferon-[y ] and interleukin-6 in colostrum of normal women. Cytokine Res 1993;12:21-4.
43. Rudloff HE, Schmalstieg FC, Mustaha AA, Palkowetz KH, Liu KS, Goldman AS. Tumor necrosis factor-a in human milk. Paediatr Res 1992;31:29-33.
44. Söder 0. Isolation of interleukin-1 from human milk. Int Arch Allergy Appl Immunol 1987;83:19-23.
45. Skansen-Saphir U. Lindfors A, Andersson U. Cytokine production in mononuclear cells of human milk studied at the single-cell level. Pediatr Res 1993;34:213-6.