Allergies, asthma, and autoimmunity are the most prevalent immune disorders and affect millions
of people worldwide. The role of prevention of these immune disorders at the level of infancy and early childhood has become an important emphasis of recent research.
The proper development of the growing infant’s immune system provides a promising avenue into prevention of these disorders. Breast milk has long been acknowledged as the optimal source of nutrition for infants, and emerging research points to its profound effect on the immune development of infants.
Immune disorders like asthma, allergies, and autoimmunity have become predominant issues in both pediatric and adult healthcare. An estimated 300 million people worldwide suffer from asthma, with 250,000 annual deaths attributed to the disease.Allergic diseases affect as many as 40 to 50 million Americans.Autoimmune diseases include more than 70 different disorders and affect approximately 5 percent of the U.S. population, or an estimated 23.5 million Americans.3 Early intervention as a means of preventing immune disorders later in life has become the subject of abundant research in recent years. Special attention must be paid to the infant’s developing immune system in order for this type of prevention to be a success. The infant is born with an immature immune system that doesn’t fully develop until several years after birth.
Mounting evidence shows that breast milk is not only an excellent source of nutrition, but it also has a profound influence on the development of the immune system and thus, the pathogenesis of asthma, allergies, and autoimmunity. This paper will focus on immune development in infants and the use of breast milk as a potential prevention of immune disorders. We will briefly review the workings of a healthy, mature immune system before discussing the developing immune system of an infant and how breast milk best promotes its proper development. Although our knowledge of the system is always advancing, the immune system in healthy adults has several distinct arms: Th0, Th1, Th2, Th3, and Th17. The T helper cells 0 (Th0) refer to mature T cells that have yet to encounter an antigen. When these naпve Th0 cells encounter an antigen, they differentiate into Th1 or Th2 cells depending on the cytokine environment. The T helper cells 1 (Th1) are recruited in response to infection and are the predominant cells used against bacterial and viral infections. T helper cells 2 (Th2) are responsible for allergic responses and responses to parasites.
Cytokines are secreted proteins that stimulate most of the biological effects in the immune system, such as the cell-mediated immunity seen in infections, predominately driven by Th1, and allergictype responses, predominately driven by Th2. These cytokines inhibit the opposing immune reaction, so a robust Th1 response to an infection inhibits a Th2 response and vice versa. Immune tolerance is characterized by a Th3 response, which involves T regulatory cells (Treg cells) and the cytokine, transforming growth factor-beta (TGF-beta). Treg cells play a major part in the regulation of immune responses, sustaining immunological self-tolerance and immune homeostasis.6 They also play a crucial role in the control of auto-reactive T-cells, making them a necessary combatant against autoimmune reactions. A Th17 immune response is associated with autoimmune conditions and the cytokine secretion of various interleukins: IL-17, IL-12 and IL-23 IL-17 is produced by Th17, which comes from a different lineage than Th1 and Th2 cells but can also stimulate the secretion of TNF-alpha and IL-1.Th17 and Treg cells have taken center stage in the discussion of autoimmune conditions.
A new category of cells named Th22 was recently discovered. Th22 enables innate epithelial immune responses.Allergies, asthma, and autoimmune conditions are associated with unresolved inflammation that contributes to the pathogenesis of these conditions. The immune system contains this system of checks and balances with responses like Th3 so that the immune system stays plastic without ever becoming stuck in one particular immune response.