The effect of added serum and glucose, and some inherent factors, on phagocytosis in vitro by milk leukocytes from several cows.

On four occasions leukocytes were obtained from mammary secretions of four cows following irritation by sterile distilled water. The effects of three levels of bovine immune serum, three levels of glucose, and combinations of these on the ability of the leukocytes to ingest staphylococci in vitro were studied. Phagocytosis was estimated by examination of stained slides prepared after four hours contact at 37 degrees C. While 1% immune serum increased the percentage of milk leukocytes ingesting staphylococci, no improvement resulted from the addition of 3% or 5%. Addition of 20mg% glucose produced a larger increase than did 1% serum, and 40 and 60mg% gave further increases. Little advantage was obtained by combining serum and glucose at any of the levels studied. Overall significant differences were found in the ability to ingest staphylococci by milk leukocytes from the four cows, and the previous observation that cells from some cows in vitro do not respond fully to added serum and glucose was confirmed. Neither of these phenomena was related to glycogen levels in blood or milk leukocytes as determined by the anthrone method, blood glucose levels, leukocyte viability, relative proportions of PMN's in circulating blood white cells, nor the amount of homologous blood serum in the mammary secretions. In two cows whose milk cells did not respond fully, very few blood PMN's were active.