[Origin and behavior of macrophages in the milk of cows with healthy and pathological udders].

Macrophages of cow milk are part of the mononucleic phagocyte system. Most of them are histiocytes which are transferred from udder tissue into milk at various stages of activity. They are variable in shape, size, and number and have certain defence and purification functions in the milk. Transformation in milk of lymphocytes to macrophages are considered possible. No hard evidence has been produced, as yet, to the repeatedly produced by means of optical light microscopy to close conglomeration of macrophages and lymphocytes in milk, which is interpreted as macrophage-lymphocyte interaction, as in immunoreactive processes. Cows with clinically intact udders were found to have in their milk between 17 and 20 per cent of macrophages, 37 or 38 per cent of polymorphonucleic leucocytes, between 13 and 20 per cent of lymphocytes as well as between 26 and 32 per cent of non-differentiable cells and cell fragments. The repair phase of acute mastitis was found to be associated with drastic decrease of milk cell counts, along with percentual rise in macrophages, caused mainly by reduction in polymorphonucleic leucocytes in the milk. With subclinical and chronic mastitis, the percentage of macrophages was found to be increased, particularly due to streptococcal infection.