The effect of breast feeding on lymphocyte subpopulations in healthy term infants at 6 months of age

Pediatr Res. 1999 May;45(5 Pt 1):648-51. doi: 10.1203/00006450-199905010-00006.


Breast milk contains many immunologically active components that influence the development of the immune system of the breast-fed infant. The purpose of this study was to investigate the difference in specific lymphocyte subsets between breast-fed and formula-fed 6-mo-old infants. Peripheral blood samples were collected from 79 breast-fed (< 120 mL formula/wk) and 69 formula-fed (breast-fed < 4 wk) infants at 6 mo. All infants had been born at term and had no known illness at the time of blood collection. Packed cells from whole blood were incubated with fluorochrome-labeled monoclonal antibodies, followed by erythrocyte lysis. Washed lymphocytes were analyzed by two-color direct immunofluorescence on a flow cytometer. The percentage of T and B lymphocytes in the peripheral blood of 6-mo-old infants was the same, regardless of feeding regimen. However, the relative frequency of natural killer (NK) cells was greater in breast-fed infants than in formula-fed infants (9.7% vs 7.1%; p < 0.001). The percentage of cells expressing CD4 was lower in breast-fed infants than in formula-fed infants (47.3% vs 50.9%; p < 0.005), and that of cells expressing CD8 was greater (18.0% vs 16.4%; p < 0.05). As a result, the CD4:CD8 ratio in breast-fed infants was lower than that in formula-fed infants (2.8 vs 3.3; p < 0.005). The absolute size of the lymphocyte subpopulations T, B, and CD8+ was the same for each of the two populations of infants. However, breast-fed infants had fewer CD4+ T cells (p < 0.05) and a greater number of NK cells (p < 0.01) than the age-matched formula-fed infants. The immunophenotypic differences between breast-fed and formula-fed infants are consistent with reported age-related changes, suggesting greater maturity in the development of the immune system of breast-fed infants.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / blood*
  • B-Lymphocytes / immunology
  • Breast Feeding*
  • CD4-CD8 Ratio
  • CD4-Positive T-Lymphocytes / immunology
  • CD8-Positive T-Lymphocytes / immunology
  • Female
  • Flow Cytometry
  • Humans
  • Infant
  • Infant Food*
  • Killer Cells, Natural / immunology
  • Lymphocyte Count
  • Lymphocyte Subsets / immunology*
  • Male
  • T-Lymphocytes / immunology
  • T-Lymphocytes, Cytotoxic / immunology
  • T-Lymphocytes, Helper-Inducer / immunology


  • Antigens, CD