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LLLI Center for Breastfeeding Information

Journal Abstract of the Month for July 2005

"Immunological components of human milk and their effect on immune development in infants"

Author: Catherine J. Field

J Nutr 05-1; 135(1):1-4.

Abstract: The immune system of the human infant, even at full term, is not fully developed and has a function unique from that of the adult human. Human milk does, in fact, have its own immune system distinct from that of both the infant and the mother. The fledgling immune system must train itself through exposure to discern the difference between harmless and harmful microbial agents. There is some evidence that the benefits of human milk to the immune system have positive effects beyond the duration of breastfeeding. The immunological support provided to human infants through their mother's milk offers an unparalled opportunity to positively foster optimal health in the growing child.

Antimicrobial properties in human milk provide resistance to disease for both mother and infant. The proportions of macrophages, neutrophils, and lymphocytes vary with the stage of lactation, but are known to positively affect T and B cell function. Cytokines and chemokines in mature human milk are an understudied area, but it is hypothesized that they may assist in the development of the infant's intestinal immune system. Additionally, the presence of minute quantities of bacterial antigens may create a controlled climate for the maturation of the infant's nascent immune response. Growth factors and hormones known to positively control the immune system have been found in human milk as well. Long-chain fatty acids and linoleic acid increase the development of lymphocytes and cytokines. Nucleotides seem to enhance systemic immune development and mucosal immunity, perhaps through improved Th1 response and differentiation of B cells.

There is strong evidence that human milk primes the infant's immune system to develop tolerance to certain foods, preventing or modulating a potential allergic response. Additionally, human milk factors seem to prevent a hyperinflammatory response to infectious agents, possibly by binding proinflammatory cytokines. Because of the complexity of human milk composition and the variance not only between women, but within any one woman's own lactational period, additional study is necessary to more fully document and understand the elements at work in human milk and how they affect the infant's immune system development.

This paper is categorized by the following keywords:

Human Milk—Immune Factors
Infant Physiology
Human Mil--Hormones
Human Milk—Growth Factors

An additional abstract of this article may be viewed at this link.

The full text of this article is available (for a fee) at

The CBI at LLLI provides additional information on immune system development and breast milk. Go to this link on the La Leche League International Web site for a compilation of research from the University of Washington. See especially Immunologic Development.
Additional Research Information from LLLI's CBI is available at this link:

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