Comparative functional study of colostral macrophages from mothers delivering preterm and at term.

Number and function of milk macrophages (MM) from 30 healthy mothers delivering preterm (mean gestational age 33 weeks) were compared with those obtained from 92 mothers with term delivery. The average concentration of MM in colostrum did not differ in the two groups: 0.55 x 10(6)/ml (preterm) and 0.42 x 10(6)/ml (term). Preterm MM showed the same activity as term MM in all three assayed functions (phagocytosis, chemotaxis and IL-1 secretion). Phagocytic activity, and impaired migratory motility and IL-1 secretion were significantly increased both in preterm and term MM in comparison with the activity in less mature blood monocytes. Thus it appears that preterm MM are, like term MM, a fully mature tissue macrophage population and therefore we suggest that with regard to MM both preterm and term colostrum are comparable, at least in the gestational age tested.