Characterization of immunocompetent cells in human milk of Han Chinese.

Immunocompetent cells in colostrum and mature breast milk (42 days after delivery) of 64 Chinese females of Han ethnic background were characterized. The total cell numbers in colostrum and mature breast milk were 593 ± 205 × 10(6)/L and 1.74 ± 0.97 × 10(6)/L, respectively. NK cell is the predominant lymphocyte subtype (12.69%). T cells in colostrum express CD40L and CD25 without stimulation, indicating memory T cells in nature. The CD45RA( +)CD45RO(+) subsets of CD4(+) T cells are present in both colostrum and mature human milk. The percentage of NK cells and the absolute number of CD4(+)CD45RO(+) T cells in colostrum of atopic mothers were significantly lower than those of mothers without atopy (P = .006 and .026, respectively). The absolute numbers of CD4( +) T lymphocytes and their expression of CD40L were significantly reduced in breast milk of mothers who had undergone cesarean section versus vaginal delivery (P < .05), indicating that atopy and cesarean delivery are associated with the phenotypes of lymphocytes in colostrum.