INTERLEUKIN-10 IN HUMAN-MILK

The concentrations of immunoreactive IL-10 in the aqueous fraction of 20 specimens of human milk obtained during the first 80 h of lactation and stored at -60 degrees C ranged from 66 to 9301 pg/mL (mean +/- SD , 3304 +/- 3127 pg/mL). IL-10 was present also in the lipid layer of m ilk. Gel filtration revealed that IL-10 was located in a high molecula r weight fraction, where certain other cytokines in human milk have be en found. In addition, immunoreactive IL-10 in milk increased after tr eatment with sodium taurocholate, Bioactive IL-10 was demonstrated by the finding that human milk inhibited [H-3]thymidine uptake by human b lood lymphocytes and that inhibition was partly overcome by concomitan t incubation with antibodies to human IL-10. IL-10 mRNA but no protein product was found in cultured human mammary epithelial cells. Some IL -10 was associated with preparations of human milk leukocytes, but the data did not suggest that the cells were producing the cytokine. Bioa ctive IL-10 in a possible protected compartment suggests that IL-10 in human milk may have immunomodulating, antiinflammatory effects on the alimentary tract of the recipient infant.