Human Milk Cells Research Articles

Chemotaxis and random migration of human milk cells

Chemotaxis and random migration of human milk cells

Characterization of Human Breast Milk Macrophages Cytostatic for Human Cell Lines

Approximately 40% of the cells in human early lactation milk possessed the characteristics of macrophages, being adherent, phagocytic, alpha napthyl acetate esterase positive, and possessing C3b and Fc receptors. These cells were also cytostatic for MDA 157, a cell line derived from a pleural effusion of human breast cancer, and HEL 23, a strain of human fetal lung fibroblasts. Investigations into the cytostatic phenomenon indicated that the cytostasis could not be mediated by macrophage-conditioned medium and that very close contact between breast milk macrophages and target cells was required. Cytostasis was not fully effective until 18 hr after the initial interaction between macrophages and target cells.

Differentiation of cord blood lymphocytes into IgA-producing cells in response to breast milk stimulatory factor

Although B cells with IgA, IgG, and IgM surface immune globulins are identified in the peripheral blood by 14 weeks gestation, only IgM differentiation has been noted when cord blood lymphocytes (CBL) were studied in vitro. These data suggest that CBL differentiation may be a regulated process. To investigate this possibility, CBLs were incubated with both pokeweed mitogen (PWM) and an IgA-specific stimulatory factor produced in culture by breast milk cells. Further, to roughly determine the molecular size of this milk cell factor, adult peripheral blood lymphocytes (PBL) were incubated with factor preparations which had been filtered to remove all proteins greater than 50,000 molecular weight. The release of IgA, IgG, and IgM by the lymphocytes in culture was quantitated using double-antibody (Ab) competitive radioimmunoassays. The milk cell factor stimulated IgA synthesis in 15 21 CBL cultures with a median IgA production of 400 ng above that measured in the unstimulated control cultures ( P < 0.001). PWM did not stimulate IgA synthesis and had minimal effect on IgG or IgM production by CBLs. In contrast, PWM stimulated a significant increase ( P < 0.001) in IgA, IgG, and IgM synthesis by PBLs. Finally, unfiltered milk cell preparations induced a significant ( P < 0.02) increase in IgA synthesis by PBLs which was abolished following removal of proteins having a molecular weight greater than 50,000. Therefore, it is postulated (1) that CBLs are capable of differentiating into immunoglobulin-producing plasma cells, (2) that CBLs differentiate in response to appropriate immunoglobulin class-specific stimuli, (3) that CBLs are unresponsive to PWM, and (4) that the soluble mediator of immunologic regulation released by human milk cells has a molecular weight greater than 50,000.

Immunoregulation by breast milk cells

Although B cells capable of synthesizing IgG and IgM have been identified in human milk, only IgA synthesis is measured in vitro. These data suggest that milk lymphocyte differentiation is a regulated process and that there may be a specific milk cell factor capable of stimulating differentiation of IgA-bearing B cells. To investigate this possibility lymphocyte/ macrophages from early (≤5 days) and late (≥8 days) milk were incubated and subsequently small aliquots of their cell-free culture media were added to peripheral blood lymphocyte cultures. The release of IgA, IgG, and IgM by the blood lymphocytes in culture was quantitated using double-antibody (Ab) competitive radioimmunoassays. The cell-free media from early (colostral) milk cell cultures significantly stimulated ( P < 0.0001) IgA synthesis and had no effect on the production of IgG or IgM. There was no effect on immunoglobulin production when the milk cell supernate came from cells isolated from more mature milk. Therefore, it is postulated (i) that a soluble mediator(s) of immunologic regulation is released by human milk cells, (ii) that this factor(s) at least in part, explains the peculiar immunologic behavior of human milk cells in vitro, (iii) that this factor(s) is released in greater amounts by colostral cells than by cells in mature milk, and (iv) that human colostrum may play a role in affecting active local immunity in the gastrointestinal tract of the recipient newborn.

Phagocytosis and killing of bacteria and yeast by human milk cells after opsonisation in aqueous phase of milk.

Macrophages and neutrophils from human milk phagocytose and kill Staphylococcus aureus and Escherichia coli in vitro after opsonisation by the aqueous phase of milk as effectively as blood leucocytes in serum. They also phagocytose Candida albicans. The overgrowth of E coli resulting from the addition of iron to cultures of the organism in the aqueous phase of milk is not influenced by the presence of cells. We conclude that the phagocytosis and killing of bacteria by milk cells may contribute to the lower incidence of infection among breast-fed than artificially fed babies.

729 IMMUNOREGULATION BY BREAST MILK CELLS

Although B cells capable of synthesizing IgG and IgM have been identified in human milk, only IgA synthesis is measured in vitro These data suggest that milk lymphocyte differentiation is a regulated process and that there may be a specific milk cell factor capable of stimulating differentiation of IgA bearing B cells.To determine if such a factor existed we cultured lymphocyte/macrophages from early(<5 days)and late(>8 days)milk and subsequently added small aliquots of their cell free culture media to peripheral blood lymphocyte(PBL)cultures. Milk cell cultures contained 2,4 and 6×106 macrophages(Φ)/ml of media and a variable number of lymphocytes while the PBL cultures contained 2×106 lymph/ml of media. The release of IgA by PBL was quantitated using double antibody radioimmunoassays. Cell free media from both early and late milk cell cultures significantly stimulated IgA synthesis.The stimulatory factor concentration was greatest in early milk cell cultures and the effect altered with increasing amounts of the regulatory factor. These data indicate that human milk cells release a regulatory factor capable of stimulating IgA synthesis by PBL and suggest a major role for colostrum in effecting active local immunity in the recipient newborn.