Considerable advances have occurred in recent years in the scientific knowledge of the benefits of breastfeeding, the mechanisms underlying these benefits, and in the clinical management of breastfeeding. This policy statement on breastfeeding replaces the 1997 policy statement of the American Academy of Pediatrics and reflects this newer knowledge and the supporting publications. The benefits of breastfeeding for the infant, the mother, and the community are summarized, and recommendations to guide the pediatrician and other health care professionals in assisting mothers in the initiation and maintenance of breastfeeding for healthy term infants and high-risk infants are presented. The policy statement delineates various ways in which pediatricians can promote, protect, and support breastfeeding not only in their individual practices but also in the hospital, medical school, community, and nation.

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Breastfeeding and the Use of Human Milk

How many child deaths can we prevent this year

Vitamins are essential constituents of our diet that have long been known to influence the immune system. Vitamins A and D have received particular attention in recent years as these vitamins have been shown to have an unexpected and crucial effect on the immune response. We present and discuss our current understanding of the essential roles of vitamins in modulating a broad range of immune processes, such as lymphocyte activation and proliferation, T-helper-cell differentiation, tissue-specific lymphocyte homing, the production of specific antibody isotypes and regulation of the immune response. Finally, we discuss the clinical potential of vitamin A and D metabolites for modulating tissue-specific immune responses and for preventing and/or treating inflammation and autoimmunity.

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Vitamin effects on the immune system: vitamins A and D take centre stage

Uropathogenic strains of Escherichia coli are characterized by the expression of distinctive bacterial properties, products, or structures referred to as virulence factors because they help the organism overcome host defenses and colonize or invade the urinary tract. Virulence factors of recognized importance in the pathogenesis of urinary tract infection (UTI) include adhesins (P fimbriae, certain other mannose-resistant adhesins, and type 1 fimbriae), the aerobactin system, hemolysin, K capsule, and resistance to serum killing. This review summarizes the virtual explosion of information regarding the epidemiology, biochemistry, mechanisms of action, and genetic basis of these urovirulence factors that has occurred in the past decade and identifies areas in need of further study. Virulence factor expression is more common among certain genetically related groups of E. coli which constitute virulent clones within the larger E. coli population. In general, the more virulence factors a strain expresses, the more severe an infection it is able to cause. Certain virulence factors specifically favor the development of pyelonephritis, others favor cystitis, and others favor asymptomatic bacteriuria. The currently defined virulence factors clearly contribute to the virulence of wild-type strains but are usually insufficient in themselves to transform an avirulent organism into a pathogen, demonstrating that other as-yet-undefined virulence properties await discovery. Virulence factor testing is a useful epidemiological and research tool but as yet has no defined clinical role. Immunological and biochemical anti-virulence factor interventions are effective in animal models of UTI and hold promise for the prevention of UTI in humans. Images

Virulence factors in Escherichia coli urinary tract infection.

Publisher Summary This chapter discusses the impact of new information concerning IgA physiology on the immune system. IgA should not be considered only as an isotype providing specific humoral protection of mucosal surfaces but as an integral component of the entire immune system. An unusual structural feature of human IgA is the heterogeneity of the molecular forms with characteristic distribution in various body fluids. Though most IgA in serum displays a typical four-polypeptide chain structure of the basic molecule with two Q and two light (L) chains, external secretions contain dimeric and tetrameric, disulfide-linked molecules associated with additional polypeptides-J (joining) chain and secretory component (SC). IgA-producing plasma cells are distributed in various lymphoid and nonlymphoid tissues and are particularly preponderant in the lamina propria of the gut; in salivary, lacrimal, and lactating mammary glands; and in the human bone marrow. IgA occurs in different body fluids in predominantly polymeric or monomeric (plasma, cerebrospinal fluid) forms with a characteristic distribution of IgAl and IgAz molecules. Under normal conditions, an absolute majority of IgA-containing cells in secretory glands and tissues also contain J chain whereas such cells in, for example, normal bone marrow does not. Staining with fluorochrome-labeled anti-J chain is enhanced by the pretreatment of alcohol-fixed tissue sections with acid urea, which leads to the exposure of masked antigenic determinants of intracellular J chain. Specialized lymphoid tissues associated with mucosal surfaces play an essential role in the induction and regulation of generalized immune responses in external secretions.

Immunoglobulin A (IgA): molecular and cellular interactions involved in IgA biosynthesis and immune response.

Variable adherence to normal human urinary-tract epithelial cells of escherichia coli strains associated with various forms of urinary-tract infection

Transfer factor in severe atopic disease

Three hundred and forty-three E. coli strains isolated from the urine of patients with asymptomatic bacteriuria (ABU), symptomatic cystitis, or pyelonephritis were analysed with regard to O group distribution and sensitivity to the bactericidal effect of normal serum. Strains of O groups 1, 2, 4, 6, 7, 16, 18 and 75 were found in 31.3% in ABU, in 58.7% in cystitis and in 79.8% in pyelonephritis. Spontaneous agglutination was noted in 45.2% of ABU, 6.5% of cystitis and 1.7% of pyelonephritis strains. The strains from patients with ABU were significantly more sensitive to the bactericidal effect of normal serum than were those from patients with symptomatic urinary tract infection. In some patients with untreated ABU, changes in the characteristics of the urinary strains isolated were noted. The strains tended to become spontaneously agglutinating as well as more sensitive to the bactericidal activity of normal serum. The strains found in patients with ABU probably had an altered cell wall compared with those found in patients with symptomatic infections such that they produce fewer symptoms and possibly be less virulent.

Asymptomatic bacteriuria in schoolgirls. II. Differences in escherichia coli causing asymptomatic bacteriuria.

Convincing studies demonstrate significant protection during breastfeeding against diarrhoea, respiratory tract infections, otitis media, bacteraemia, bacterial meningitis, botulism, urinary tract infections and necrotizing enterocolitis. There is also good evidence for enhanced protection for years after the termination of breastfeeding against Haemophilus influenzae type b infections, otitis media, diarrhoea, respiratory tract infections and wheezing bronchitis. In some reports breastfeeding has also improved vaccine responses. Several studies show that milk may actively stimulate the immune system of the offspring via transfer of anti-idiotypic antibodies and lymphocytes. This may explain why breastfeeding diminishes the risk of developing coeliac disease. Some investigations suggest that there may also be a similar effect on allergic diseases and autoimmune diseases, as well as inflammatory bowel diseases and certain tumours. This needs to be confirmed.

L. Å. Hanson

Papers

Variable adherence to normal human urinary-tract epithelial cells of escherichia coli strains associated with various forms of urinary-tract infection

Transfer factor in severe atopic disease

Asymptomatic bacteriuria in schoolgirls. II. Differences in escherichia coli causing asymptomatic bacteriuria.

Human milk and host defence: immediate and long-term effects.

Adhesion to normal human uroepithelial cells of Escherichia coli from children with various forms of urinary tract infection.