Leucocytes and their function in breast milk: 8

The leucocytes in the breast milk of 14 mothers 2-5 days following delivery were studied.Total white, cell counts ranged from 16.000/ml to 2.400.000/ml.The proportion of cell types varied in the different milk samples:Macrophages (mono-cytes) made up 30-85%,polymorphonuclear neutrophils 10-70% and lymphocytes 5-15%.In order to test milk-leucocytes function an assay of antibody-dependent cellular cytotoxicity which depends exclusively upon monocytes and polymorphonu-clears as the effector cells was applied.Blood group A ery-throcytes (RBC) from healthy human donors treated with hyper-immune anti-A serum were used as target cells.Haemolysis was quantitated by a release of radioactivity from RBC pre-labelled with 51Cr-chromate.Comparison with the cytotoxicity elicited by similar or even lower monocyte numbers taken from the peripheral blood of adults or neonates showed that of milk monocytes to be significantly lower.Since phagocytosis has been shown to be important (p<0.001) in the lysis of sensitized A, red cells perhaps milk monocytes are not so active because they are loaded with fat granules.